The Pennsylvania State University. The Graduate School. College of Health and Human Development THE EFFECTS OF GENDER AND LOWER EXTREMITY ALIGNMENT ON

Transcription

1 The Pennsylvania State University The Graduate School College of Health and Human Development THE EFFECTS OF GENDER AND LOWER EXTREMITY ALIGNMENT ON THE KINEMATICS OF THREE FUNCTIONAL TASKS A Thesis in Kinesiology by Jennifer Michele Medina 2006 Jennifer Michele Medina Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy August 2006

2 The thesis of Jennifer Michele Medina was reviewed and approved* by the following: Jay Hertel Adjunct Assistant Professor of Kinesiology Thesis Adviser Co-Chair of Committee Craig R. Denegar Associate Professor of Athletic Training & Kinesiology Co-Chair of Committee William E. Buckley Professor of Exercise and Sport Science and Health Education Samuel W. Monismith Associate Professor of Health Education Philip E. Martin Professor of Kinesiology Head of the Department of Kinesiology *Signatures are on file in the Graduate School.

3 iii ABSTRACT Research in sports medicine has focused on identifying the risk factors that tend to increase the risk of knee injury in fes compared to s. Several intrinsic and extrinsic factors have been identified to explain, in part, this gender discrepancy in knee injury risk. While most research has focused on gender as the discriminating factor, these present studies were an attempt to identify kinematic differences that are independent of gender and that are more related to structure. The purposes of these studies are to 1) compare the effects of gender on lower extremity alignment, 2) compare the effects of gender on lower extremity kinematics during 3 functional tasks, 3) to examine the relationships between lower extremity alignment and kinematics, and 4) to compare groups of extremes of alignment to an alignment group in a middle range in regards to lower extremity kinematics. Twenty-four healthy, active subjects between the ages of (12 s; height = ± 7.5 m; weight = 83.8 ± 17.6 kg and 12 fes; height = ± 5.7 m; weight = 61.6 ± 6.3 kg) volunteered for study. Subjects had a history of at least 1 year of participation in competitive basketball. Measurement of six lower extremity alignments (navicular drop, tibial varum, quadriceps angle, genu recurvatum, pelvic tilt, and femoral anteversion) was performed on each subject using previously described methods. Each subject then performed 5 trials of 3 novel, but sport-related, functional tasks. The 3 functional tasks were a maximal vertical jump, a sidestep cutting maneuver, and a jump stop. These 3 tasks were designed to mimic the most common sport-related mechanisms

4 iv of injury for the anterior cruciate ligament injury. Three-dimensional kinematic data for the hip and knee were collected. The measures that were analyzed were joint angles for the hip and knee in the sagittal, frontal, and transverse planes. Specific kinematic variables that were analyzed were joint angle at initial contact, peak angle, time-to-peak angle, and total change in joint angle for each of the three functional tasks. For Study #1, a comparison of gender and lower extremity alignments was performed to ensure that the sample population demonstrated alignment patterns similar to commonly accepted gender differences. A comparison of s and fes was then made to examine the effects of gender on the specific kinematic measures listed above. Statistical analysis revealed that there was a gender difference for the measures of lower extremity alignment. Fes demonstrated greater q-angle, genu recurvatum, and femoral anteversion compared to s. There was no difference between s and fes for navicular drop, tibial varum, or pelvic tilt. For the analysis of the effect of gender on lower extremity kinematics, there was a single, significant kinematic descriptor for each of the three functional tasks. All 3 significant kinematic variables were related directly to hip motion. For Study #2, relationships between lower extremity alignments and kinematics were evaluated. Bivariate correlations were performed to analyze for these associations. A second analysis compared the extremes of alignment to a middle range of alignment for effect on lower extremity kinematics during the 3 tasks. This was an attempt to identify if the significant relationships as observed in the correlational analysis would be revealed

5 v as significant differences between groups of lower extremity alignment. Though there were significant correlations between certain lower extremity alignments and kinematics, a majority of the significant correlations were relatively small with most alignments explaining less than 30% of the variance of any of the kinematic measures. No correlational trends were directly confirmed when each lower extremity alignment was divided into thirds of least, middle, and greatest degree of alignment. Lower extremity alignment does contribute to alterations in kinematics during functional tasks. The kinematics that are altered based on lower extremity alignment tend to be altered towards imparting more stress on the knee. There are certain lower extremity alignments that more fes tend to demonstrate (larger q-angles, more genu recurvatum, and greater femoral anteversion) and these alignments are one of the many factors associated with the increase in knee injury rates for fes. Future research should focus on the identification of risk factors for knee injury that may be demonstrated by s or fes. Rather than examining gender specific differences, research should target on the identification of the specific causes of the differences in movement patterns between s and fes rather than implicating gender alone. By identifying specific risk factors, new prevention strategies can be developed and refined, with the goal of reducing the risk of injury to all individuals.

6 vi TABLE OF CONTENTS List of Tables List of Figures Acknowledgements viii ix x Chapter 1. INTRODUCTION 1 Statement of the Problem 3 Statement of the Purposes 3 Significance 4 Research Hypotheses 5 Limitations 6 Assumptions 7 Operational Definitions 8 Chapter 2. REVIEW OF THE LITERATURE 10 Lower Extremity Alignments 10 Correlated Postures 11 Compensatory Postures 11 Navicular Drop 12 Tibial Varum 13 Quadriceps Angle 14 Genu recurvatum 15 Femoral Anteversion 16 Pelvic Tilt 16 Gender and Functional Task Performance 19 Kinematics During Functional Tasks 22 Methods of Reducing Error 24 Lower Extremity Alignment and Movement Patterns 25 Kinematics and Injury 26 Cutting Maneuvers 27 Landing From a Jump 28 Deceleration 30 Conclusion 32 Chapter 3. THE EFFECTS OF GENDER ON LOWER EXTREMITY KINEMATICS FOR THREE FUNCTIONAL TASKS 33 Abstract 34 Introduction 35 Methods 37 Results 44 Discussion 46 Conclusions 51

7 vii Chapter 4. THE EFFECTS OF LOWER EXTREMITY ALIGNMENT ON KINEMATICS FOR THREE FUNCTIONAL TASKS 54 Abstract 55 Introduction 57 Methods 59 Results 67 Discussion 71 Conclusions 79 Chapter 5. CONCLUSIONS 85 Bibliography 89 Appendix A: Additional Methods 96 Appendix B: Data Tables 101 Appendix C: Informed Consent Forms 105 Appendix D: Plug-in-Gait Form 108 Appendix E: Lower Extremity Alignment Data Form 109

8 viii LIST OF TABLES Table 1: Gender Comparisons of Lower Extremity Alignments 52 Table 2: Table 3: Table 4: Table 5: Significant Gender Differences in Kinematics for Vertical Jump task 53 Gender Comparisons of All Lower Extremity Kinematics for the Vertical Jump 99 Gender Comparisons of All Lower Extremity Kinematics for the Sidestep Cut 100 Gender Comparisons of All Lower Extremity Kinematics for the Jump Stop 101 Table 6: Cut Points for the Thirds of Lower Extremity Alignment 81 Table 7: Table 8: Table 9: Significant Correlations between Lower Extremity Alignments and Kinematics 82 Nonsignificant 1x3 ANOVA results of the significant general linear mode comparing Genu Recurvatum and Peak Knee Angles during the sidestep cutting task 83 Significant relationships between extremes of Lower Extremity Alignment and Kinematics 84 Table 10: Families of Similar Kinematic Variables 104

9 ix LIST OF FIGURES Figure 1: Measurement of Navicular Drop 94 Figure 2: Measurement of Tibial Varum 94 Figure 3: Measurement of Quadriceps Angle 95 Figure 4: Measurement of Genu Recurvatum 95 Figure 5: Measurement of Femoral Anteversion 96 Figure 6: Measurement of Pelvic Tilt 96 Figure 7: Maximal Vertical Jump 97 Figure 8: Sidestep Cutting Maneuver 97 Figure 9: Jump Stop 97 Figure 10: Retroreflective Marker Placement 98

10 x ACKNOWLEDGEMENTS I would like to thank the co-chairs of my committee: Jay Hertel for his mentorship and friendship, and Craig Denegar for his advice over the years and for opening my eyes to evidence-based clinical research. I would also like to thank my committee members Bill Buckley and Sam Monismith for their advice and input into this project. I would like to thank Joe Hart for his help with the technological aspects of this project and for his laptop. I would also like to acknowledge the people at Kluge Children s Research Center for use of the lab, especially Dave Carmines and Barbara Leech. I also thank my friends at Penn State and the University of Virginia for their help, support and willingness to go out for drinks during the best and worst times. Most of all I would like to thank all my family; especially my parents Robert and Judy for teaching me too follow my own path, and for loving and supporting me the whole way, my sister Emily for being everything a sister should be, and Pat McKeon, my best friend and soulmate for truly sharing with me every aspect of this process.

11 xi EPIGRAPH Oh, joy! Rapture! I ve got a brain! - Scarecrow, The Wizard of Oz Life s like a movie, write your own ending - Kermit the Frog, The Muppet Movie Fight on my merry men all I'm a little wounded, but I am not slain; I will lay me down for to bleed a while Then I'll rise and fight with you again. - Anonymous

12 1 Chapter 1 INTRODUCTION Traditional physical examination of gait and posture often includes a screening for bilateral symmetry of alignment of the lower extremities. Asymmetry within an individual is normal, as are variations between individuals. 1 When any particular alignment is outside the normal range, it can be termed a malalignment. When evaluating injuries, it is common practice for clinicians to look for malalignment throughout the kinetic chain. Of concern to the clinician are the implications of malalignment to causation of injury. There is a potential relationship between static malalignment and both acute and overuse injuries, 2-9 however, the relationship is variant among individuals. Certain alignments are commonly measured as part of a lower extremity examination. In particular, the measures of navicular drop, tibial varum, quadriceps angle, genu recurvatum, femoral anteversion, and pelvic tilt are often included in that evaluation. Accepted measurement techniques 3, 4, 6, have been developed for each of these measures and are typically used by clinicians. Malalignments in one or more of these areas have been identified as potential factors that increase the risk of n acute injuries, particularly noncontact anterior cruciate ligament (ACL) injuries, as well as chronic injuries to the lower extremity. There also tend to be normal differences of alignment between men and women although there are few published data for normal ranges. Fes tend to demonstrate larger quadriceps angles, more genu recurvatum, more

13 2 anterior pelvic tilt, and greater femoral anteversion. These differences have been examined to help explain gender discrepancies in injury rates and differences in movement patterns. Three-dimensional motion analysis is a common method of capturing human movement for research purposes. By fixing reflective markers on specific anatomical landmarks, the skeletal system can be recreated and biomechanical features can be recorded and measured during functional tasks. Several studies have demonstrated gender differences for neuromuscular, kinetic, and kinematics characteristics in regards to movement patterns and these differences are used to explain, in part, discrepancies in injury rates between the genders. GENDER DIFFERENCES: Is it gender specific or alignment specific? There has been considerable discussion about lower extremity alignments and how they may relate to gender and injury. It is assumed that it is specifically gender that affects movement patterns and kinematics. However, it is unknown if the differences between s and fes in regards to performance of functional tasks are related specifically to gender or if task performances more closely related the anatomical and structural presentation of the individual. HOW DOES LOWER EXTREMITY ALIGNMENT AFFECT PERFORMANCE DURING FUNCTIONAL TASKS?

14 3 It is expected that extremes of alignment may be a predisposition to certain acute and chronic injuries. It is also accepted that certain kinematics may increase the injurious forces imparted on the joints. It is unknown if a lower extremity alignment that is within a functional range affects kinematics or how these alignment variations, when they occur, can predispose to injury. STATEMENT OF THE PROBLEM It is unknown how static lower extremity alignment correlates to movement patterns. While it has been demonstrated that s and fes often perform dynamic tasks differently, the source of these differences is unknown. It is also unknown how lower extremity alignment affects movement patterns and kinematics during athletic tasks. Currently, there is no successful method of screening and identifying athletes at increased risk for ACL injury that is practical, 28, 29 both from a cost and time perspective. To date, the only successful method of identifying athletes at risk was though use 3-dimensional motion analysis. 29 Unfortunately, this method is neither cost nor time effective to clinicians. The monetary cost of a stereophotogrammetric system and the time required to perform motion analysis does not favor screening with this method. There is a need for practical and accurate identification of risk factors that are actually associated with ACL injury, in order to better recommend injury prevention programs for all athletes who are predisposed to injury.

15 4 STATEMENT OF THE PURPOSES The objective of these studies is to compare 6 common measures of lower extremity static alignment (navicular drop, tibial varum, quadriceps angle (q-angle), genu recurvatum, femoral anteversion, and pelvic tilt) with dynamic joint angles in the sagittal, frontal, and transverse planes during the functional, sport-related tasks of a maximal vertical jump, a sidestep cutting maneuver, and a jump stop. Specific kinematic variables to be examined at the hip and knee are joint angles at initial ground contact, peak angles, times-to-peak angles, and total joint angle change. The purposes of these studies are to 1) evaluate the effect of gender on lower extremity alignment in a healthy population, 2) to evaluate the effect of gender on lower extremity kinematics during 3 functional tasks, 3) evaluate correlations between lower extremity alignments and lower extremity kinematics during 3 functional tasks, and 4) evaluate effect of the extremes of alignment, i.e. values outside the middle range, on lower extremity kinematics during 3 functional tasks. SIGNIFICANCE These studies may provide insight into gender-specific movement patterns. More importantly these studies may provide an identification of specific alignments that alter movement patterns, rather than simply explaining alterations by gender alone. Additionally, identifying a lower extremity alignment or series of alignments that may increase the risk of ACL injury during functional, sports-related tasks could provide

16 5 clinicians with a cost-effective screening method and aid in the recommendation for a particular athlete to take part in an ACL injury prevention program. RESEARCH HYPOTHESES Based on information provided from previous studies, these are the hypotheses for the present studies: Study #1 There will be a significant difference between genders in regards to certain measures of lower extremity alignment. Based on previous studies, fes will likely demonstrate larger values for quadriceps angle, genu recurvatum, pelvic tilt, and femoral anteversion. There will be a significant difference between s and fes in regards to certain lower extremity kinematics. Fes will use landing accommodation strategies that tend to place a greater degree of stress on the knee in the frontal and transverse planes compared to s. Additionally, fes will demonstrate more erect landing compared to s. Study #2 There will be significant correlations between some measures of lower extremity alignments and measures of lower extremity kinematics. In particular, alignment

17 6 measures more typically demonstrated in fes and the kinematics described as more typical of fe movement patterns. Extremes of lower extremity alignment will contribute more to alterations in lower extremity kinematics than alignment values within the middle ranges. There will be a significant difference between groups with the least and most alignment as compared to groups with a more normal alignment. In addition, these will mirror significant trends that are observed in the correlational analyses. LIMITATIONS The tasks are functional in nature, but are still anticipated and not spontaneous. Although functional tasks better capture the true nature of task performance, anticipated performance of functional tasks may not entirely represent the true performance of these tasks in a real-life situation and is a limitation of using laboratory motion analysis to describe real-life movement. There is a conflict between constraining the task in order to make it reproducible between subjects and allowing the subject to perform the task unimpeded The subjects are healthy, active young adults; therefore results can only be generalized to that population. The retroreflective markers are applied to the skin; soft tissue artifact introduces error that can be minimized, but not eliminated completed.

18 7 Although the motion analysis system allows for recording of all three planes, the frontal and transverse planes tend to be more unreliable as compared to the sagittal. There is error associated with the techniques for measurement of the lower extremity alignments. ASSUMPTIONS Subjects performed the tasks as they would in an athletic environment Subjects performed the tasks with maximal effort Failed and repeated trials did not fatigue the subject or contribute significantly to alteration of task performance

19 8 OPERATIONAL DEFINITIONS ACL anterior cruciate ligament Femoral anteversion the angle of rotation of the femur in the transverse plane Frontal plane (also, Y direction) adduction is denoted as positive, abduction as negative Genu reucruvatum the angle of knee hyperextension created by the femur and the fibula in the sagittal plane Jump stop a forward moving approach with an abrupt halt, a plant on the right foot and 30 o change of direction to the left with a shift back to a two-foot stance and jump straight up into the air. This task is similar to the motion basketball player would perform after receiving a pass and taking a jump shot. LE lower extremity Malalignment abnormal joint alignment or deformity within a bone or series of bones that is a cause of pathology or dysfunction. MTSS medial tibial stress syndrome Navicular drop a static measure of subtalar pronation, which is a dynamic motion. It is calculated as the difference in height of the navicular tuberosity from the floor while the subject is seated and then in standing OA osteoarthritis PFPS patellofemoral pain syndrome Pelvic tilt degree of anterior tilt of the pelvis in the sagittal plane Pose the position and orientation of a body segment in space

20 9 Quadriceps angle (q-angle) the angle between the line of pull created by quadriceps muscles and the alignment of the patellar tendon as it inserts on the tibial tuberosity Sagittal plane (also, X direction) flexion is denoted as positive, extension as negative Sidestep cut a 45 o approach to the force plate, plant on the right foot, and a 45 o change in the opposite direction with no foot crossover Tibial varum the angle at which the distal third of the tibia diverges laterally from the vertical in the frontal plane Transverse plane (also, Z direction) internal rotation is denoted as positive, external rotation is negative Vertical jump a foot take-off/ two-foot landing vertical jump with a two-arm reach for maximal height.

21 10 Chapter 2 REVIEW OF THE LITERATURE I. LOWER EXTREMITY ALIGNMENTS Traditional physical examination of gait and posture often includes a screening for bilateral symmetry of the lower extremities, although asymmetry within an individual, and variations between individuals, is normal. 1 Every individual will demonstrate static alignment postures that are based on genetics, previous injury, and loading patterns. When any particular alignment is outside the normal range, it can be termed a malalignment. Riegger-Krugh et al 1 defined malalignments as an abnormal joint alignment or deformity within a bone that is a cause of pathology or dysfunction. The pathology associated with a malalignment may be directly located at the site of the malalignment or may be located at distant sites. 30 An abnormal alignment may also correlate with other malalignments as a method of compensation. It is common practice for clinicians to look for compensatory malalignment throughout the kinetic chain. There is the traditional belief that an extreme of one alignment will cause a compensatory posture somewhere else in the kinetic chain. One of the most wellknown series of lower extremity (LE) compensations is the miserable malalignment syndrome, a combination of hyperpronation at the foot, increased tibial external torsion, and increased femoral anteversion. These compensatory postures may occur in response to other excessive malalignments or to optimize gait and neuromuscular function, normalize cosmetic appearance, or improve foot contact with ground. 1 Concomitantly,

22 11 these postures may be a predisposition to acute and overuse injuries. Riegger-Krugh et al 1 described lower extremity correlational and compensational postures based on clinical observations and individual measurements. CORRELATED POSTURES Correlated postures have been defined as those motions or postures that are naturally related to the motion or posture imposed at the joint with the malalignment 1 For example, a greater angle of genu recurvatum would typically be correlated with excessive anterior pelvic tilt. 1 With excessive genu recurvatum, the femoral heads will be positioned more anteriorly. To align properly with the acetabulae, the pelvis must tilt more anteriorly to meet the femoral heads. Similarly, a more anterior pelvic tilt may force the knee into more hyperextension, again because of the alignment of the hip joints. It is important to note here that it is not known which malalignment is considered the cause and which is the affected. COMPENSATORY POSTURES Compensatory motions and postures are defined as those that occur in response to a malalignment. 1 These tend to minimize the appearance of a deformity and allow gait to be relatively normal. Unlike correlational postures which tend to follow specific patterns, compensatory postures may or may not be present. For example, an individual may compensate for a malalignment, but it is unpredictable as to the resulting compensation. For example, to compensate for excessive femoral anteversion, an individual may demonstrate a relatively high degree of tibial external rotation. Femoral anteversion

23 12 results in an internal rotation of the lower extremity. The compensatory external tibial rotation counteracts the femoral anteversion and the lower extremity remains wellaligned. On the other hand, the compensatory external rotation of the tibia may not be present, and that individual may demonstrate a more pigeon-toed, or toed-in, appearance. Assessment of lower extremity alalignment often includes measures of navicular drop, tibial varum, tibial torsion, quadriceps angle, genu recurvatum, femoral anteversion, and anterior pelvic tilt Navicular Drop Navicular drop is a static measure of subtalar pronation, a dynamic motion. 11 Two positional measures are taken to calculate navicular drop. The first measurement is the distance from the navicular tuberosity to the floor, taken while the subject is seated and non-weight bearing. The second measurement is taken in with the subject standing in a weight bearing position. Navicular drop is calculated as the difference in arch height between the seated and standing measurements. The intrarater reliability for this method of measuring navicular drop has been reported at ICC = 0.61 to A greater static navicular drop has been correlated to increased subtalar pronation. 11 Excessive subtalar pronation tends to increase the amount of tibial internal rotation in relation to the femur and has been implicated as a predisposing factor for certain chronic injuries such as medial tibial stress syndrome (MTSS), plantar fasciitis, and patellofemoral pain syndrome (PFPS). 8, 9 Additionally, excessive navicular drop has been associated with acute injuries, in particular, injury to the anterior cruciate ligament

24 13 (ACL). It was reported that greater navicular drop was a significant predictor of ACL injury history and that this was independent of gender. 7 Increased navicular drop has been correlated to greater anterior tibial translation at the knee in sagittal plane. 6 Anterior translation of the tibia stresses the ACL and a large navicular drop may therefore increase the stress on the ACL. Although there is an increased incidence of noncontact ACL injury in fes, Tillman et al 5 no reported difference between s and fes in subtalar joint range of motion. Tibial Varum Tibial varum is the angle at which the distal third of the tibia diverges laterally from the 3, 4, 9 vertical in the frontal plane. Lohmann et al 3 reported that the measurement of tibial varum can have a high intrarater reliability (ICC =.83) if the technique is practiced and skillfully executed. McPoil et al 2 reported an even higher intrarater reliability (ICC =.96) for the technique used for measuring tibial varum in the present study. On a side note, those researchers 2 claimed that the distal third measurement is actually more accurately described as tibiofibular varum, however, for purposes of this manuscript the term tibial varum will be used to describe the angle of the distal third of the leg. A more varus alignment tends to incline more laterally, as moving from distal to proximal. Similar to other lower extremity alignments, excessive tibial varum is traditionally viewed as having a relationship with other malalignments and with increased risk of acute and chronic injuries. Under normal circumstances, there is a 1:1 ratio between tibial varum and calcaneal eversion. 3 If the distal tibia is positioned in a more varus position, the calcaneus must evert more to maintain appropriate heel contact in weight

25 14 bearing. More pronation is then required in order to get to footflat. Excessive tibial varum has been reported as both a risk factor for both PFPS 8 and as a common physical presentation in a group of individuals with overuse injuries of the foot and leg. 4 Greater degrees of tibial varum may also contribute knee osteoarthritis by increasing compression forces at the medial joint compartment. 9 In regards to acute injury, the relationship between tibial varum and other lower extremity malalignments may increase risk of injury at the knee. As stated previously, greater tibial varum is associated with greater subtalar pronation 3, which has been associated with increased anterior tibial translation 6 which may increase the risk of ACL injury, and navicular drop which is a predictor of ACL injury history 7. For these reasons, excessive tibial varum may place more stress on the ACL. Quadriceps Angle Quadriceps angle (Q-angle) is defined as the angle between the line of pull created by quadriceps muscles and the alignment of the patellar tendon as it inserts on the tibial tuberosity. 5 Typically, fes have a larger Q-angle than s because of the greater hip-to-knee ratios that more fes demonstrate. 8 In regards to injury at the knee, it is thought that a larger Q-angle increases the valgus stress at the knee, increasing risk of both acute and chronic injuries. A common mechanism of ACL injury is collapse of the knee into flexion and external rotation of the tibia, with a concurrent and excessive valgus position at the knee. A larger Q-angle increases the valgus forces at the knee by creating a longer moment arm between the patella and tibia in the frontal plane at the knee, which potentially increases the risk of ACL injury. Greater Q-angle is likely

26 15 related to chronic conditions, such as PFPS. A larger than normal Q-angle will laterally direct the line of action for the quadriceps and pull the patella further into the lateral edge of the patellar groove of the femur. 9 In a cadaveric study 32, it was demonstrated that increasing the Q-angle increased the contact pressures between the lateral patella and femur which increases the likelihood of PFPS. Genu Recurvatum Genu recurvatum is the angle of knee hyperextension created by the femur and the fibula in the sagittal plane. 6 Genu recurvatum exists when the subject is able to hyperextend beyond 0 o. Hyperextension of the knee will tend to stress the ACL more 10, as there is more anterior translation of the tibia. The ACL may be slightly impinged within the intercondylar notch when in full extension 33, increasing shear on the ACL. Genu recurvatum was the only abnormal physical examination feature common among a sample of collegiate and fe athletes who suffered a noncontact ACL injury. 34 In a separate sample of fe athletes 35, it was reported that values of genu recurvatum for those who had a history of ACL injury were larger when compared to those who had never suffered an ACL rupture. Additionally, one of the more common mechanisms for noncontact ACL injury is hyperextension of the knee. 34 When in slight hyperextension, the hamstrings are at decreased mechanical advantage. This will diminish their ability to dynamically stabilize the knee and prevent anterior tibial translation, and there will be a greater reliance on the ACL to stabilize the knee.

27 16 Femoral Anteversion Femoral anteversion, the angle of rotation of the femur in the transverse plane, is assessed 9, 10, 13 by the Craig Test. Comparison of this technique with intraoperative measurements, demonstrated this method to be superior even to radiologic techniques for determining femoral anteversion in children about to undergo surgery at the hip. 13 Nyland et al 36 reported that athletic fes with a greater degree of femoral anteversion demonstrated a relatively smaller peak EMG amplitudes for the vastus medialis and gluteus medius compared to athletic fes with lesser degrees of femoral anteversion. This suggests that with greater degrees of femoral anteversion, there is a decrease in dynamic stabilization provided by muscles that control the hip and knee. Gluteus medius weakness has been associated with potential increases in ACL injury 36 and patellofemoral problems 8, 37, as there is an inability to control the knee as it is moving through eccentric adduction, which may increase valgus forces at the knee. As reported in a case series, two patients with PFPS demonstrated no obvious malalignment at the knee or tracking problems, but did demonstrate a weakness of the hip abductors and a subsequent lack of control of the hips in the frontal plane. 38 Vastus medialis weakness is also related to 8, 37 PFPS. The vastus lateralis is relatively unchecked and pulls the patella excessively lateral, increasing the contact forces between the patella and femur. These muscular weaknesses may be directly related to femoral anteversion position. Pelvic Tilt Pelvic tilt is the degree of anterior tilt of the pelvis in the sagittal plane. 14,15 It is thought that a more pronounced anterior pelvic tilt will reduce the mechanical advantage of the

28 17 hamstrings, and increase the degree of femoral anteversion, as well as the degree of genu recurvatum. Posture with a greater anterior pelvic tilt may increase the risk of ACL 7, 35 injury. With greater anterior tilt, the hamstrings are positioned in a lengthened position, which may decrease the mechanical advantage and lengthen the electromechanical delay to meaningful contraction of those muscles. By decreasing the mechanical advantage of the hamstrings and the concurrent increase in mechanical advantage of the hip flexors, there is a diminished level of dynamic stability at the knee in response to anterior tibial translation. Increasing the anterior pelvic tilt may cause a greater degree of femoral anteversion and increase the valgus forces at the knee. A larger pelvic tilt may also increase the degree of genu recurvatum and therefore, increase the stresses placed on the ACL. Hertel et al 7 demonstrated that fes, regardless of ACL injury history, tend to have a greater degree of anterior pelvic tilt than s. It was also reported that greater anterior pelvic tilt was associated with history of ACL rupture and that this was independent of gender. 7 Loudon et al 35 also reported that a higher degree of anterior pelvic tilt was associated with history of ACL injury in fe athletes. Additionally, with the increase in femoral anteversion in response to greater anterior pelvic tilt, there is an increased risk of chronic conditions. Genu valgum and Q-angle will likely be larger, increasing the risk of chronic patellofemoral problems. 39 While lower extremity malalignment does not always directly contribute to pathology, a connection is often drawn between the malalignment and the condition of interest. A recent study 40 demonstrated that excessive knee valgus or varus were a significant contributing factor for osteoarthritis (OA) of the knee. Though often related to injury, it

29 18 is important to note that lower extremity malalignment is not necessarily a cause of lower extremity injury. Individuals with any particular malalignment may or may not suffer injury. Likewise, an individual may be develop an injury that is normally associated with malalignment and not exhibit any of these postural problems. It is anecdotally assumed that different measures of lower extremity malalignment are interrelated; however, there is little statistical evidence to substantiate this claim. 9 Based on unpublished data of malalignment patterns among healthy intercollegiate athletes 41, there is a statistically quantifiable relationship between certain measures of lower extremity malalignment; and that measures of malalignment at the foot and knee are significantly related to malalignments at the hip and pelvis. The contribution of any one malalignment to another was, however, relatively small. It is necessary for clinicians to perform a comprehensive lower extremity malalignment screening to identify contributions that may lead to imbalances or injury because the different malalignment measures are not strongly correlated to each other. The assumption that the influence of one malalignment will significantly affect another joint or body segment is flawed, as is the practice of focusing on one particular malalignment as the singular cause of a particular injury. It is theorized that extremes of alignment may increase risk of injury by increasing the moments that act on a particular joint, and that the ligament will be abnormally stressed. It is also of concern that there will be abnormal contact pressures within the joint, a theorized predisposition for osteoarthritis. Of concern to the clinician are the

30 19 implications of malalignment to causation of injury. There is a potential relationship between static malalignment and overuse injuries. An excessively abnormal lower extremity alignment may cause abnormal stress patterns at the joint. 9 Lower extremity malalignments are often implicated in certain overuse injuries and they are often the first item addressed when treating these condition. For example, Witvrouw et al 37 claimed that correction of malalignment is a key component to treating PFPS. In an unpublished study 42, subjects with a history of MTSS demonstrated greater femoral anteversion and q- angle as compared to matched controls. Of these measurable alignments, it has been observed that fes tend to demonstrate larger q-angles, more genu recurvatum, femoral anteversion, and pelvic tilt, even when within normal ranges. There has also been considerable discussion about malalignments and how they may relate to gender and injury. The differences in lower extremity alignments are one of the many factors that are studied to help explain the discrepancy in injury rates between s and fes. II. GENDER & FUNCTIONAL TASK PERFORMANCE An accommodation strategies paradigm has been proposed to model the relationship between a stressor and the body s response to accommodate that stressor. 43 The body s accommodation strategies are in place to help maintain system homeostasis and to 43, 44 prevent injury. Two different mechanisms are utilized by the individual to prevent injury. The first is a feedback mechanism, which is a reflexive response that occurs after sensory detection of the perturbation. 44 It is a mechanism to identify changes that affect

31 20 the sensorimotor system and to provide corrections to prevent falls or injuries. However, the feedback mechanism alone is not fast enough to provide stability and prevent collapse. 45 There is also a feedforward mechanism, an anticipatory effect that occurs before sensory detection of the perturbation. 44 When the system is perturbed, there is preparatory contraction of the muscles to stiffen the joints, a protective response to prevent injury The preparatory contraction also provides stability and control of joint moments to prevent collapse, which is a performance response The purpose of 44, 45 these mechanisms is to provide efficient neuromuscular control. When landing from a jump, neuromuscular recruitment patterns and recruitment velocity of the thigh muscles play a role in providing stiffness and dynamic stability at the knee. 48 There is a preparatory and reflexive co-contraction of the quadriceps and hamstrings to stiffen the area around the joint to prevent injury. 49 The preparatory action is the neuromuscular activity before foot contact. Reflexive action is the activity after foot contact. A recommended method of determining lower extremity muscle activation during a functional task is to divide the task into phases to specifically determine preparatory and reflexive muscle activity. 50 Croce et al 51 examined the muscular cocontraction of the quadriceps and hamstrings in response to a jump landing task. In that study, there was no statistical difference between s and fes in regards to muscle activation. Both s and fes demonstrated mature landing patterns with appropriate co-contraction of the hamstrings and quadriceps. In contrast, post-pubescent and fe groups both demonstrated greater hamstring-quadriceps co-contraction

32 21 than pre-pubescent s and fes. Prepubescent subjects demonstrated greater quadriceps activation compared to the hamstrings in response to the drop jump task. Muscular preactivation provides stability and control of the joint moments at the knee. There is a need for efficient neuromuscular control to create this dynamic joint stiffness and protective stability. Muscle strength, as well as a balance between antagonist muscle groups, is necessary for preventing injury. To protect the ACL, the hamstrings contract to assist in preventing anterior translation of the tibia. 48 A study by Horita et al 47 demonstrated that s tended to show greater muscle stiffness in both the hamstrings and quadriceps than fes in response to perturbation, a reaction that provides more protection for the knee. An unbalanced or irregular response may predispose an individual to injury. Hewett et al 52 demonstrated that fes tend to have an unbalanced quadriceps to hamstrings strength ratio when compared to their counterparts. They found a 2:1 unilateral quadriceps to hamstrings strength ratio in fes and a 3:2 ratio in s. 52 This quadriceps-dominant protection strategy may diminish the hamstrings ability to assist the ACL by providing dynamic stabilization of the knee. 53 Huston et al 54 reported an altered recruitment pattern response to anterior translation in fe subjects. In that study, fes tended to recruit the quadriceps, then the hamstrings, during an anterior translation perturbation of the tibia. Males tended to recruit their hamstrings followed by their quadriceps, which may actually increase the strain on the ACL. The altered activation pattern seen in the fe group was not demonstrated by Shultz et al 25 who found that both s and fes tended to activate the hamstrings first in response to perturbation; however, fes had a much shorter latency period before activating the quadriceps. This response may result in the hamstrings not reaching full firing capacity

33 22 before the quadriceps offset that force. The result is a decreased summative response of the hamstrings and increased strain on the ACL. The factors that cause this altered firing pattern are unknown. It may relate to structural differences between s and fes. Fes tend to have a greater degree of anterior pelvic tilt. This puts the hamstrings on a stretch while pre-shortening the quadriceps. Pre-shortening a muscle group decreases the electromechanical delay (EMD) for that group, and the muscles contract faster. 55 EMD, which has both central and peripheral contributions, is the total time it takes the electrical signal for contraction to reach the muscle and for the muscle to develop force. This increase in EMD will result in a slower time to meaningful contraction. In an early study by Bell and Jacobs 56, fes demonstrated an increased EMD during a maximal volitional contraction of the elbow flexors. Drop landing tasks, although widely used, may not capture the true activity of the muscle. The drop landing standardizes for drop height, however, does not take individual subject muscular capabilities into account. For example, one subject may consider a drop height more difficult to land from and may activate muscles differently than a subject who views the task as easy. It is recommended that a more functional task in order to capture the true activity of the extremities of interest. 51 III. KINEMATICS DURING FUNCTIONAL TASKS The kinematics of a functional, biomechanical task can be captured using 3-dimensional optoelectric stereophotogrammetry. 57 Using a reflective marker system, the position and orientation, or pose, of the extremity in space can be tracked. 58 Motion analysis involves

34 23 the use of a system of markers placed on the surface of specific locations of a body segment or segments. When placed properly, the markers represent the skeleton and can be tracked during functional tasks. A multiple camera system is used to locate the markers at their instantaneous position in space and digitally recreates the trajectory of the markers, building a model of the subject s motion. Motion is recorded as pose of one segment in relation to another adjacent segment. 58 There is the option to use active markers or passive markers to track human movement. Active, light-emitting markers are advantageous as they are more easily tracked and allow for more accurate reconstruction. 59 However, there are two considerable disadvantages associated with using active markers; each disadvantage limits the number of markers that can be placed. Active markers require a power source and each marker must pulse at a different frequency in order to be identified. 59 For this, batteries and/or wires are required, which can become cumbersome and alter the way a subject performs the task being studied. Passive, retroreflective markers are a common alternative to active markers. Passive markers reflect infrared illumination from a light emitting diodes mounted on the lens of each camera. 59 Passive markers tend to be slightly less accurate than active markers; however, do not require a local power source and allow for more uninhibited task performance. 60 There are two main sources of error associated with motion analysis, errors based on instrumentation and errors associated with soft tissue artifact. 59 Stereophotogrammetry can be used to recreate the kinematics of a functional task in the three spatial dimensions,

35 24 however, these three planes are not equal with respect to the degree of error that is recorded with the signal of interest. 61 In the sagittal plane, there is a relative confidence in the accuracy of results. The frontal plane is not as accurate; and though stereophotogrammetry can capture the rotational motion in the transverse plane, it is the least accurate. 61 Soft tissue artifact is the main contributing source of error 62, particularly in the transverse plane. 61 It is important to reduce sources of error and to minimize error propagation. Error reduction can be accomplished by minimizing the movement of the skin where the markers are attached. Since the markers are fixed to the skin and not rigidly to the skeletal system 59, it is important to position the markers over areas of minimal soft tissue thickness and skin movement. Error associated with instrumentation comes from noise received into the system and from lens distortion, and generally carries a frequency much higher than that of human motion. 59 This type of error is relatively easy to filter out using a low pass filter. Error due to soft tissue artifact is more problematic, as it is a result of human motion and carries a frequency that is equal to that which is of interest. METHODS OF REDUCING ERROR There is a risk that the markers will be covered momentarily during a task. Accepted marker locations are used for the reduced likelihood of the camera losing a marker and have been demonstrated to best capture the motions being studied. 63 Additionally, these marker locations are over bony landmarks, making palpation and positioning standardized and reproducible. 63 Additionally, positioning bony landmarks allows for

36 25 minimization of soft tissue artifact as discussed previously. Marker redundancy is another approach for maximizing marker visibility. Using more markers than is necessary creates redundancy in the marker system. Redundancy of marker placement allows for reconstruction of a marker that is lost to the cameras during testing. The use of multiple cameras also ensures better capture of the task. Although recreation of 3D movement requires only two cameras, the use of multiple cameras also reduces the risk of a marker becoming obscured and improves the probability that at least two cameras will see each marker. 59 Although there is error associated with stereophotogrammetry, it is used frequently in gait analysis studies. Some motion analysis studies also attempt to associate human movement patterns with positions and forces that cause injury. In particular, there has been a push to understand the kinematics associated with noncontact 17, 20, 28, 29, ACL injuries. LOWER EXTREMITY ALIGNMENT and MOVEMENT PATTERNS Multiple studies have demonstrated differences in movement patterns and landing strategies between s and fes. Differing responses to functional performance, both kinematics and neuromuscular response, have been reported. The most logical theory to explain this gender difference is that there is a neuromuscular component to these strategies that differs by gender. Whether it is the purely neuromuscular system or if there is a mechanical component that is affecting the neuromuscular system is unknown.

37 26 It is believed that s have a different confidence interval of normative values for certain lower extremity alignments as compared to fes; however, there will be individuals of both genders who will fall into the overlap of confidence intervals for some or all lower extremity alignments. The question is if these individuals will display movement behavior that is indicative of gender or of the lower extremity alignments. There have been reported differences between s and fes in kinematics during response to functional tasks such as greater hip and knee adduction, stiffer and more erect landing posture, and more internal rotation of the hip. 16, 17, 19, 20, 26, 28, 64, 69, 70, 72 In one gait analysis study 26, fe recreational runners demonstrated significantly different lower extremity kinematics from runners in the frontal and transverse planes. Peak hip adduction, hip internal rotation, and knee abduction angles were larger in the fe runners as compared to the runners. The kinematic difference between s and fes that are displayed for functional tasks is another factor that is studied in the search for an explanation of higher injury rates in women. KINEMATICS & INJURY Three of the most common mechanisms for noncontact ACL (NCACL) injury are during a lateral pivoting or cutting maneuver, when landing from a jump, or during 67, 73 deceleration. Though these maneuvers are repeated innumerate times by an individual during athletic participation, one instance will suddenly cause injury. Many studies attempt to recreate these mechanisms and analyze the kinematics and kinetics of

38 27 tasks in order to gain a better understanding of these mechanisms that unpredictably cause an ACL injury. Cutting Maneuver One of the most common mechanisms of injury for the ACL is during a cutting maneuver. Both sidestep cutting and crossover cutting maneuvers increase forces at the knee in the coronal and transverse plane when compared to straightforward running. 67 The greater valgus moments at the knee during these types of maneuvers are more difficult for the stabilizing musculature around the knee to counteract. The combination of dynamic knee valgus and flexion, internal rotation of the femur, and relative external rotation of the tibia with the foot planted has been termed the position of no return the position from which the dynamic stabilizers of the knee cannot overcome external forces and the additional torque is transmitted to other structures. 74 The excessive valgus moment imposed on the knee in this position increases shear forces on the ACL. With regards to gender and kinematics during functional tasks, fe adolescents demonstrated greater knee valgus in a neutral, ready position and at initial contact in response to an unanticipated cutting task compared to adolescents, however there was no significant difference between genders with regard to maximal knee valgus angles. 17 Since there was no difference between the genders at maximal valgus angles, it is questionable if greater valgus in ready and initial contact positions translate into increased risk of injury during cutting. In contrast, McLean et al 64 reported a difference between genders in regards to valgus moments at the knee in response to a sidestep

39 28 cutting task. Fes tended to demonstrate higher peak valgus moments during the cutting task compared to s when normalized for height and leg length. Additionally, peak knee valgus moment was more sensitive to the amount of initial internal hip rotation and knee valgus angle in fes. The observed association between peak knee valgus moment and peak knee valgus angle, initial hip flexion angle, and initial internal rotation angle in response to a sidestepping task. 64 While the claim that there may be a difference in neuromuscular recruitment patterns that is related to the difference between the genders in knee valgus, there was also an observed increase in maximal ankle eversion and decrease in ankle inversion in the fe athletes compared to athletes. 17 There is a concern that increased eversion and associated tibial internal rotation could increase the valgus stress at the knee. As discussed previously, greater subtalar pronation has been reported as a significant predictor of ACL injury history. 7 Landing from a Jump Landing from a jump is another common mechanism of noncontact ACL injury. There have been several studies 16, 18, 19, 28, 29, 72, 75, 76 that have examined the difference between the genderes in regards to landing from a jump. In a study of high school basketball players, fe athletes demonstrated greater total knee valgus and greater maximum knee valgus compared to athletes in response to a drop jump landing. 28 Stiffer, less knee flexion A coupling relationship was demonstrated between flexion-extension and varus-valgus movement patterns during stair climbing. 77 Individuals with greater knee flexion angles

40 29 also performed the stair ascending/descending task with more varus knee angles. Individuals who stepped with less knee flexion tended to compensate by exhibiting greater knee valgus in order to accommodate the ground reaction forces. This less-flexed knee accommodation strategy has also been demonstrated in fes as compared to s during functional landing tasks. Fe collegiate athletes have demonstrated a stiffer and more erect landing posture at initial contact when compared to collegiate 16, 19 athletes. Accommodation of the ground reaction forces by increasing the valgus angle at the knee could be a predisposition for a knee injury. Although both groups in the one study 16 demonstrated similar vertical ground reaction forces and imposed forces absorbed at the knee, the more erect posture brings the knee closer to full extension and potentially, hyperextension. In the second study 19, this was true for both a single-leg landing and single-leg forward hop tasks. Hyperextension of the knee stresses the ACL. Additionally, a more straight-legged landing may reduce the efficiency of the hamstrings, the dynamic stabilizers of the knee. Valgus-Varus Motion Fe collegiate athletes demonstrated more excursion in the coronal plane when compared to athletes in response to both medially and laterally directed singlelegged drop landing. 72 As with sidestep cutting, fes demonstrated significantly more knee abduction that s at initial contact and at peak abduction angle. Similar results have been reported by Ford 28 ; fe high school athletes responded to drop vertical jump landings with greater knee valgus at initial contact and also demonstrated greater peak knee valgus than athletes. Hewett 22 also reported similar results for the

41 30 drop jump landing task, however, this was only seen in postpubertal fes compared to postpubertal s. There were no differences seen between prepubertal s and fes or between early pubertal s and fes in that study. External rotation of the shank Fe collegiate athletes demonstrated more hip internal rotation and less concurrent shank internal rotation than athletes for a single leg forward hop task. 19 This increase in opposing rotations at the knee stresses the ACL and a contributor to the position of no return. Deceleration Knee hyperextension during deceleration is a potential mechanism of injury. In downhill skiing, a common mechanism of noncontact ACL injury occurs in response to the individual losing balance, but not falling. As the individual sits back and the upper body decelerates, the lower legs maintain connection with the surface and continue to slide down the hill. The ensuing forces are transmitted to the knee, where the tibia glides anteriorly on the femur. Injury occurs when the stress is chiefly absorbed by the ACL. Deceleration injuries also occur when the body suddenly decelerates and the forces are absorbed at the knee. An example of a common mechanism of injury occurs when the individual jumps and plants both feet in front and hyperextends the knee during that action, stressing the ACL.

42 31 There was an observed association between peak knee valgus moment and peak knee valgus angle, initial hip flexion angle, and initial internal rotation angle in response to a sidestepping task. 64 The measure of interest in that study was the dynamic position of the knee, however, static posture is also related to valgus forces imposed on the knee. Lower extremity malalignments may contribute to acute injury at the knee based on the forces that place stress on the anterior cruciate ligament. In a prospective study of college athletes, baseline measurements of dynamic knee valgus position and knee valgus moments in response to a drop jump landing were taken. 29 These athletes were subsequently monitored for injuries during sport participation. It was observed that greater peak valgus angles correlated with larger dynamic knee valgus moments during drop vertical jump (DVJ). 29 Additionally, it was observed that athletes who went on to rupture their ACL from a noncontact mechanism, demonstrated greater initial valgus angles and greater peak valgus angles than athletes who did not suffer an ACL injury. 29 The results of that study demonstrate that greater peak valgus angles correlated with larger knee valgus moments during DVJ, and that these measures are predictors of ACL injury. Drop landing tasks, although widely used, may not capture the true characteristics of landing from jumps during athletic participation. The drop landing standardizes for drop height, however, does not take individual capabilities into account. For example, one subject may consider a drop height more difficult from which to land and may accommodate differently than a subject who views the task as easy. Croce et al 51 recommended a more functional task in order to capture the true nature of the subject s

43 32 landing strategy. Unanticipated task performance may increase the risk of injury by increasing the forces at the knee. 78 Anticipated performance of functional tasks may not entirely represent the true performance of these tasks in a real-life situation. 78 This represents a limitation of using motion analysis to describe real-life movement. IV. CONCLUSION Currently, there is no successful method of screening and identifying athletes at increased risk for ACL injury that is also practical 28, 29, both from a cost and time perspective. Correlations between 2D and 3D kinematics for valgus motion at the knee correlate moderately well. 66 Frontal plane, 2D analysis is a simpler method to measuring peak knee valgus angles during dynamic tasks and identifying individuals at risk for knee injuries. However, this simplified method still is not readily available to all clinicians. Static measurements of lower extremity alignment may provide a cost effective and space-sensitive method for predicting peak knee and hip angles. To date, the only successful method of accurately predicting athletes at risk was though use 3D motion analysis. 29 The monetary cost of a stereophotogrammetric system and the time required to perform motion analysis does not favor screening with this method. There is a need for practical and accurate identification of risk factors that are actually associated with ACL injury. Identifying malalignments or series of malalignments that may increase the risk of ACL injury during functional, sports-related tasks could provide clinicians with a cost-effective screening method and aid in the recommendation for a particular athlete to take part in an ACL injury prevention program.

44 33 Chapter 3 THE EFFECTS OF GENDER ON LOWER EXTREMITY KINEMATICS FOR THREE FUNCTIONAL TASKS

45 34 ABSTRACT Introduction: There is a discrepancy between s and fes in regards to lower extremity injury rates. It is common knowledge that s and fes tend to display different normative values for certain lower extremity alignments. Multiple studies have demonstrated gender differences for movement patterns and landing strategies. While there is information regarding the difference between the genders and kinematics, there is only speculation as to the influence on those kinematic differences and it is unknown if it is gender or the specific alignments that are typically displayed by the genders that contribute to these differences. Purpose: The purpose of this study was to evaluate the effect of gender on lower extremity alignments and kinematics during 3 sport-related, functional tasks. Subjects: Twenty-four healthy subjects (12 s; height = ± 7.5 cm; weight = 83.8 ± 17.6 kg and 12 fes; height = ± 5.7 cm; weight = 61.6 ± 6.3 kg) volunteered for participation in this study. Methods: Six common measures of lower extremity posture (navicular drop, tibial varum, quadriceps angle, genu recurvatum, pelvic tilt, and femoral anteversion) were collected using previously established methods. Measures were performed on the subject s right lower extremity only. Three-dimensional motion analysis was used to measure kinematic data. Specific kinematic descriptors examined were joint angle at initial contact, peak angle, time-topeak, and total joint angle change. Results: The fe group in this study demonstrated larger q-angle, genu recurvatum, and femoral anteversion compared to s. There were few kinematic descriptors that were significantly different between s and fes and the three kinematic descriptors that were significantly different were all directly related to the hip. For the vertical jump and jump stop, fes demonstrated

46 35 significantly less peak hip abduction than s. For the sidestep cut, fes demonstrated significantly more hip internal rotation at initial contact as compared to s. Conclusions: There were observed differences between genders for lower extremity alignments and certain kinematic measures. How gender and kinematic performance are specifically related is unknown. Future research should target on the identification of the specific causes of the differences in movement patterns between s and fes rather than implicating gender alone. INTRODUCTION There is a discrepancy between s and fes in regards to lower extremity injury rates. Several intrinsic and extrinsic factors have been examined in order to explain this discrepancy. No specific difference between genders has been identified to explain all contribution to the greater incidence of lower extremity injuries in fes. One intrinsic factor with obvious differences between the genders is lower extremity alignments. It is common knowledge that s and fes tend to display different normative values for certain lower extremity alignments. Of the measurable lower extremity alignments, fes tend to demonstrate larger q-angles and more genu recurvatum as compared to s. There has been considerable discussion about lower extremity alignments and how they may relate to gender and injury. A second factor used to explain the discrepancy in injury rates between s and fes is related to the kinematic performance of sports-related movement patterns. Multiple studies have demonstrated differences in movement patterns and landing

47 36 strategies between s and fes. Differing responses to functional performance, both kinematics and neuromuscular response, have been reported. It has been reported that fes tend to demonstrate more hip adduction and internal rotation, more knee adduction, and a stiffer landing compared to s, and these kinematics are all theorized 16, 17, 19, 26, 28, 64, 72 to be predisposing factors for injury. The most logical theory to explain this gender difference is that there is a neuromuscular component to these strategies that differs by gender. Whether it is purely the neuromuscular system or if there is a mechanical component that is affecting the neuromuscular system is unknown. While there is information regarding the difference between the genders and kinematics, there is only speculation as to the influence on those kinematic differences and it is unknown if it is gender or the specific alignments that are typically displayed by the genders contribute to these differences. The purpose of this study is to evaluate the effect of gender on lower extremity alignments for this population and more importantly, to evaluate the effect gender on lower extremity kinematics during 3 functional tasks. Based on previous observations, it is hypothesized that there will be a difference between s and fes in regards to certain lower extremity alignments in this study. There will most likely be a difference between genders for q-angle, genu recurvatum, pelvic tilt, and femoral anteversion. Based on this information, it is hypothesized that there will be a difference between s and fes in regard to certain lower extremity kinematics that can be explained by the particular alignment differences. Specific kinematics to be examined are joint angle at initial contact, peak angle, time-to-peak, and total joint angle change. Gender

48 37 differences will be related to a more erect landing in fes as compared to s and the use of landing accommodation strategies that places a greater degree of stress on the knee in the frontal and transverse planes compared to s. METHODS Subjects Twenty-four healthy, active subjects (12 s; height = ± 7.5 cm; weight = 83.8 ± 17.6 kg and 12 fes; height = ± 5.7 cm; weight = 61.6 ± 6.3 kg) volunteered for participation in this study. Inclusion criteria required that each subject to be between the ages of 18-30, with at least 1 year of competitive participation in the sport of basketball. Exclusion criteria required that each subject had no reported history of serious knee injury, and was free from any acute orthopedic injury to the back or lower extremity for at least 1 month prior to testing. It was also required that subjects never participated in any type of ACL injury prevention program or were currently participating in general plyometric training. Subjects who met the inclusion and exclusion criteria were asked to participate. The subjects who agreed received and signed an informed consent, which was approved by the Institutional Review Board of the University of Virginia for use in this study. Lower Extremity Alignment Data Collection Six measures of lower extremity posture were collected using previously established methods. Measures were performed on the subject s right lower extremity only.

49 38 NAVICULAR DROP Navicular drop was determined using methods described by Bonci 10 and measured with a vernier height gauge (Mitutoyo America Corporation, Aurora, Il). The central point of the navicular tuberosity was located and marked. An initial measurement was taken with the subject seated, with both feet on the floor, unweighted and in subtalar neutral. The unweighted navicular position was the distance from the floor to the marked point on the navicular tuberosity. The subject then stood, keeping equal pressure on both feet and the measurement was repeated. Navicular drop was calculated as the difference between the two measurements. This method has been reported to have an intrarater reliability of.78 to Figure 1 demonstrates the methods for measuring navicular drop. TIBIAL VARUM Tibial varum was determined as described by Tomaro 4, with the subject in a weightbearing, double-limb stance and equal weight on each foot. The posterior aspect of the shank was bisected two-thirds of the length of the tibia from the medial joint line to the medial malleolus. A second point was marked at the point bisecting the widest point from the medial malleolus to the lateral malleolus. Tibial varum is the angle at which the distal third of the tibia diverges from the perpendicular as measured with a standard goniometer. 4 The goniometer was modified with addition of a fluid level to improve the accuracy of measurement for this study. This measurement was taken without controlling for subtalar neutral. By not controlling for subtalar neutral, the position of the foot in relation to the shank is more functional. The interrater reliability has been

50 39 reported as high as ICC=.83 with sufficient practice by the clinician. 3 Figure 2 demonstrates the methods for measuring tibial varum. QUADRICEPS ANGLE Quadriceps angle (Q-angle) was measured as described in Tomisch et al. 12 With the subject in standing, the central point of the patella was located as a line running from the anterior superior iliac spine (ASIS) that bisects the patella. The central point of the tibial tuberosity was also located and a second line drawn from that point to bisect the patella. Q-angle was determined as the acute angle made by those lines. This measurement was performed in standing in order to record a more functional representation of Q-angle. Special care was taken to assure that the subject s quadriceps were in a relaxed position, as contraction of the quadriceps would affect the position of the patella Intratester reliability for standing q-angle is reported as.75 in well-trained testers. 79 Figure 3 demonstrates the methods for measuring q-angle. GENU RECURVATUM Genu recurvatum is the angle of knee hyperextension created by the femur and the fibula in the sagittal plane. This measurement was performed as described by Trimble et al. 6 While in standing, each subject was asked to extend the knee as fully as possible. In some cases, subjects reached hyperextension. The measurement was performed using standard goniometer. This method has been reported to have an intrarater reliability of Figure 4 demonstrates the methods for measuring genu recurvatum.

51 40 FEMORAL ANTEVERSION 10, 13 The measurement of femoral anteversion was performed as previously described. The greater trochanter of the femur was located by palpation while the subject lay prone. With the knee flexed, the hip was passively internally and externally rotated until the greater trochanter could be palpated at its most lateral point. Femoral anteversion was determined with a standard goniometer as the acute angle formed by the tibia and an imaginary vertical line. Comparison of this technique with intraoperative measurements by Ruwe et al 13, demonstrated this method to be superior to radiologic techniques for determining femoral anteversion in children about to undergo surgery at the hip. Figure 5 demonstrates the methods for measuring femoral anteversion. PELVIC TILT Pelvic tilt was determined as described by Petrone 14 using a PALpation Meter (Performance Attainment Associates, St. Paul, MN). The anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) were located and marked. One arm of the PALMeter was placed on the each landmark. Pelvic tilt was measured as the degree of anterior tilt of the pelvis in the sagittal plane. This method has been reported to be highly reliable (ICC =.99). 15 Figure 6 demonstrates the methods for measuring pelvic tilt. All measurements were performed by the same investigator (JMM). Alignment data were recorded by hand and transferred to a spreadsheet.

52 41 Functional tasks MAXIMAL VERTICAL JUMP Each subject performed 5 trials of a one foot take-off/ two-foot landing vertical jump with a two-arm reach for maximal height. Subjects were instructed to take one step with the right leg and takeoff from that same leg and land on both feet. Figure 7 demonstrates the performance of the maximal vertical jump. SIDESTEP CUT Each subject performed 5 trials of a sidestep cutting task. The subject was asked to perform this task within an approximate 10 x 5 m space. The subject approached the force plate from the left at a 45 o angle, planted and then performed a 90 o change of direction, leaving the force plate at 45 o towards the left. If the subject performed a crossover cut or rounded out the direction change, the trial was discarded and repeated. Figure 8 demonstrates the performance of the sidestep cut. JUMP STOP Each subject performed 5 trials of a jump stop task. The subject was asked to start at one end of the runway. The subject sprinted forward to a predetermined spot on the force plate, at which point the subject came to an abrupt halt, planting on the right foot and changing directions 30 o to the left. The subject then shifted back to a two-foot stance and jumped straight up in the air. This task is similar to the motion a basketball player would perform after receiving a pass and taking a jump shot. Figure 9 demonstrates the performance of the jump stop.

53 42 Each subject was to allowed to practice tasks until comfortable with performing the tasks in a repeatable fashion. The subject then performed five trials of each of these functional, sport-related tasks. All tasks were performed barefoot. Kinematics for these tasks were recorded by three-dimensional optoelectric stereophotogrammetry for each attempt for this task. Five trials of each task were collected and averaged for a single representation of each task for each subject. If performance of any task was overtly altered because of force plate targeting, the trial was discarded and repeated. Kinematic Analysis Three dimensional motion analysis was used to capture lower extremity kinematic data. Kinematic data were collected using a passive, 8-camera, 3-D VICON motion analysis system (Oxford Metrics Ltd.; Oxford, UK). Camera calibration errors were all below 1.3 mm. Marker trajectories were sampled at a rate of 120 Hz and a 30-frame fill gap threshold was set to reconstruct lost markers. Marker trajectories were filtered through a low-pass Woltering digital filter with predicted MSE value of 30 and a cutoff frequency of 15Hz. Static reproducibility and wand visibility was above 60%. Kinematic data were synchronized with vertical ground reaction force-sensitive floor data as recorded by one of four imbedded force plates (Kistler Instrument Corp.; Winterthur, Switzerland and AMTI; Watertown MA) and was used to identify the time at initial contact with the ground with respect to task performance. Hip and knee joint centers for the right and left leg were reconstructed using the Plug-in- Gait modeler (VICON Oxford, UK Peak Performance Technologies, Inc, CO). Hip and

54 43 knee joint angles for the right leg were calculated and included in the analysis. Neutral hip and knee alignment was defined as 0. Relative flexion, internal rotation, and adduction were subsequently denoted as positive, whereas extension, external rotation, and abduction were negative. Each subject was fitted with 16 retroreflective markers (14-mm diameter) at specific anatomical locations (see Figure 10). Three-dimensional optoelectric stereophotogrammetry was used to capture the kinematic characteristics for 5 successful trials of each task. Failed trials, which included improper task performance by the subject or a technological system error, were discarded and the trial was repeated. Statistical Analysis A multivariate analysis of variance was performed to compare the effect of gender on the static lower extremity alignment measures for this sample. In the event of a significant MANOVA, individual 1x2 ANOVAs were run to identify the specific significant differences between genders. Means and standard deviations were calculated to describe specific differences. The kinematics were divided into families of similar variables. The families were defined by the anatomic location (i.e. hip or knee) and type of kinematic descriptor (i.e. joint angle at initial contact, peak angle, time-to-peak, and total joint angle change). Refer to Appendix B, Table 10 for details of kinematic families. Separate MANOVAs were performed to evaluate the effect of gender on each family of kinematic variables. These

55 44 were run for each of the three tasks. In the event of significant MANOVA results, individual t-tests were performed to identify specific differences. Means and standard errors of the means for each variable were calculated to specifically describe differences. One MANOVA was used to determine the effect of gender ( and fe) on each dependent variable (individual joint angles and rotations). All statistical analyses were conducted in SPSS 13.0 (SPSS for Windows, SPSS Science Inc, Chicago, Ill). An alpha level was set a priori at.05 to determine statistical significance in all analyses. RESULTS Comparison of Gender and Lower Extremity Alignments There was a significant multivariate difference (P =.01) between s and fes in this sample for 3 of the 6 measures of lower extremity alignment. Fes demonstrated greater angles for q-angle (P =.009), genu recurvatum (P =.021), and femoral anteversion (P =.005). There was no difference between genders for the other lower extremity measures. Means and standard deviations for each alignment measure are present in Table [1]. Comparison of Gender and Lower Extremity Kinematics VERTICAL JUMP There was one significant difference between the genders for the vertical jump task.. Males achieved greater hip abduction compared to fes (P =.005). There were no other significant kinematic differences between genders for this task.

56 45 SIDESTEP CUT There was one significant difference between s and fes for kinematics of the cutting task. Males tended to perform the cut with more hip internal rotation at initial contact compared to fes (P =.009). There were no other differences between genders for kinematics during the sidestep cutting task. JUMP STOP There was one significant difference between genders for the jump stop task. Males demonstrated greater angles of peak hip abduction than fes (P =.003). There were no other differences between genders for the kinematics of the jump stop task. Details of significant results are presented in Table [2]. DISCUSSION The purpose of this study was to examine the relationship between gender, lower extremity alignments, and kinematics of three functional, sport-related tasks. The first analysis examined relationships between gender and a series of commonly measured lower extremity alignments. The second analysis was used to examine how the gender may affect 3-dimnesional kinematics during functional tasks. It is common knowledge that s and fes tend to display different normative values in lower extremity alignments. While there is a breadth of information regarding the difference between the genders and kinematics, there is only speculation as to the influence on those kinematic

57 46 differences and it is unknown if it is gender or the specific alignments that are typically displayed by the genders that contribute to these differences. Initially, I compared the lower extremity alignments between s and fes in a healthy adult population. This examination revealed differences between s and fes for q-angle, genu recurvatum, and femoral anteversion. This has become an accepted belief. There were no significant difference between s and fes for navicular drop, tibial varum, or pelvic tilt. The purpose of making the gender comparison was to ensure that these groups displayed values that are within the accepted ranges, or if one or both groups fell outside average values. Analysis of the lower extremity alignments revealed means that were within the accepted ranges, therefore we can say that the second part of the analysis is a reasonable examination of a normal population and that the kinematics demonstrated for these tasks represent a similar population. We then compared of the 3-dimensional kinematics at the hip and knee for s and fes during three functional tasks. Previous studies have been used to demonstrate a 16, 17, difference between genders for landing strategies and other types of functional tasks. 19, 26, 28, 64, 72 Lower extremity kinematic differences between s and fes are one of the factors that have been examined to explain, in part, the discrepancy in injury rates between genders, however, the relationship between gender and kinematic differences is unknown. Examining novel, but sport-related, functional tasks may shed light on the specifics of kinematic differences.

58 47 PEAK HIP ABDUCTION ANGLE For both vertical jump and jump stop tasks, a difference between s and fes existed for peak hip abduction angle during the vertical jump task. Both groups were in a position of abduction, however, fes were in significantly lesser degree of abduction compared to s. Similar results were previously reported as fe recreational runners demonstrated significantly greater peak hip adduction as compared to runners kinematics from runners in the frontal and transverse planes. Peak hip adduction, hip internal rotation, and knee abduction angles were larger in the fe runners as compared to the runners. 26 While a specific correlation cannot be made to the task performance and injury, less abduction may be potentially harmful to the knee because this position tends to increase the valgus forces at the knee. Hip position in the frontal plane is believed to influence moments at the knee in the frontal plane, with greater hip adduction correlating to an increase in knee valgus forces. 64 HIP INTERNAL ROTATION ANGULAR VELOCITY For the cutting task, there was a significant difference between s and fes for hip internal rotation angles at initial contact. Males came into contact with considerably more hip internal rotation than fes. However, for hip internal rotation, there was no difference between the genders for peak angles or time-to-peak. From an angular velocity perspective, fes were achieving a much higher angular velocity than s. When looking at the kinematics and kinetics of an increased velocity of the joint motion, the forces on the joint increase with increased velocity.

59 48 Angular velocity is a measure that may capture kinematics that may predispose to injury. Faster angular velocities may indicate a greater amount of stress on joints in two ways. An accommodation strategies paradigm has been proposed to model the relationship between a stressor and the body s response to accommodate that stressor 43. The body s accommodation strategies are in place to help maintain system homeostasis and to prevent injury 43, 44 The preparatory contraction of periarticular muscles in response to perturbation provides stability and control of joint moments to prevent collapse The 44, 45 purpose is to provide efficient neuromuscular control. There is a need for efficient neuromuscular control to create dynamic joint stiffness and protective stability. Electromechanical delay (EMD) is the total time it takes the electrical signal for contraction to reach the muscle and for the muscle to develop force. Faster angular velocities may be detrimental to the joint because of the shorter time to reach a meaningful and protective contraction of the periarticular musculature before the joint reaches its peak angle. Without meaningful contraction of the muscles around the joint, the forces of the perturbation are absorbed fully in the static structures (ligaments, joint capsule, or articular cartilage) of the joint. Faster angular velocity may also affect the material properties of the articular connective tissue. Connective tissue is viscoelastic and therefore, its response to loading is ratedependent. When a load is applied, the tissue deforms to accommodate those forces. As the rate of loading increases, the tissue responds by becoming stiffer. This increased stiffness protects the joint by allowing less deformation to the structure, however, if external forces exceed the yield point, permanent damage to the connective tissue occurs.

60 49 Faster angular velocity may affect the joint structures causing an increased stiffness, which will initially provide protection the structures, but will also shorten the time needed to reach the yield point where permanent damage occurs.

61 50 LIMITATIONS Lower extremity malalignments are often implicated in certain overuse injuries and they are often the first item addressed when treating these condition. Though often related to injury, it is important to note that excessive lower extremity malalignment is not necessarily a cause of injury. Individuals with any particular alignment may or may not suffer injury. Likewise, an individual may be develop an injury that is normally associated with malalignments and not exhibit any of these postural problems. Data collection for this study was performed on a healthy population with no lower extremity injuries. While lower extremity alignments may affect kinematics, in this healthy population, the kinematics do not appear to be pathological for this population, and we cannot conclude that the kinematics displayed by these groups actually contribute to injury in the general population. Three-dimensional motion analysis is commonly utilized for biomechanical studies, however, there is error associated with this type of analysis. 59 Motion analysis can be used to recreate the kinematics of a functional task in the three spatial dimensions, however, these three planes are not equal with respect to the degree of error that is recorded with the signal of interest. 61 While there is a relative confidence in the accuracy of results in the sagittal plane, the frontal and transverse plane tend to be less accurate. 61 Since the markers are fixed to the skin and not rigidly to the skeletal system 59, soft tissue artifact is the main contributing source of error 61,62 and is difficult to filter out as it is a result of human motion and carries a frequency that is equal to that which is of interest.

62 51 Though the tasks designed for this study are functional in nature, they were described to the subject in full before performance of the task, and therefore, fully anticipated and not spontaneous. There is a conflict between constraining the task in order to make it reproducible between subjects and allowing the subject to perform the task unimpeded. Pre-designed functional tasks are good for capturing motions similar to sport-related performance 51, however, the anticipated performance of functional tasks may not entirely represent the true performance of these tasks in a real-life situation. 78 CONCLUSIONS This study was an attempt to identify specific kinematic differences between the genders for three functional tasks and was performed on a sample that was representative of healthy, active adults with normal body alignments. The results of the comparison of gender and lower extremity alignment corroborated previous studies in that the fe group in this study demonstrated larger q-angle, genu recurvatum, and femoral anteversion compared to s. In contrast, there were no gender differences for anterior pelvic tilt although previous evidence has suggested that fes tend to display greater pelvic tilt than s. While there were few kinematic descriptors that were significantly different between s and fes, the three kinematic descriptors that were significantly different were all directly related to the hip. There was an observed difference between gender and lower extremity alignments between gender and certain kinematic measures. How gender and kinematic performance are specifically related is unknown. Future research should target on the identification of the specific causes of the

63 52 differences in movement patterns between s and fes rather than implicating gender alone.

64 53 Table 1: Gender Comparisons of Lower Extremity Alignments Males Fes P- value 95% Confidence Intervals Navicular drop (cm) 1.1 ± ± ,.35 Tibial varum ( o ) 5.3 ± ± , 1.98 Q angle ( o ) 11.0 ± ± * -6.60, Genu Recurvatum ( o ) 3.3 ± ± * -6.50, -.62 Pelvic Tilt ( o ) 9.0 ± ± , Femoral Anteversion ( o ) 7.5 ± ± * ,

65 54 Table 2: Significant Gender Differences in Kinematics for All Tasks Kinematics Males Fes P-value 95% Confidence Intervals Means ± SD Means ± SD VERTICAL JUMP Peak Hip Adduction Angle ± ± , -1.7 CUT Hip Internal Rotation at Initial Contact 16.7 ± ± , 28.8 JUMP STOP Peak Hip Adduction Angle ± ± , -2.5 Negative values represent Hip Abduction

66 55 Chapter 4 THE EFFECTS OF LOWER EXTREMITY ALIGNMENT ON KINEMATICS FOR THREE FUNCTIONAL TASKS

67 56 ABSTRACT Introduction: There is a discrepancy between s and fes in regards to lower extremity injury rates. Kinematic performance between s and fes is one of the extrinsic factors that have been examined to explain, in part, the discrepancy in injury rates between the genders. It is theorized that alignment will affect lower kinematics and that extremes of alignment may increase risk of injury by increasing the range of motion and thus the moments that act on a particular joint, and that ligaments may be abnormally stressed. There is only speculation as to the influence on those kinematic differences and it is unknown if it is gender or the specific alignments that are typically displayed by the genders that contribute to these differences. Purpose: The purpose of this study is to examine the relationship between the magnitude of lower extremity alignment with kinematic measures of the hip and knee during the performance of three functional, sportrelated tasks. Subjects: Twenty-four healthy subjects (12 s; height = ± 7.5 cm; weight = 83.8 ± 17.6 kg and 12 fes; height = ± 5.7 cm; weight = 61.6 ± 6.3 kg) volunteered for participation in this study. Methods: Six common measures of lower extremity posture (navicular drop, tibial varum, quadriceps angle, genu recurvatum, pelvic tilt, and femoral anteversion) were collected using previously established methods. Measures were performed on the subject s right lower extremity only. For each lower extremity alignment, limbs were divided into lower(1), middle(2), and upper(3) thirds. The lower subgroup represented limbs with the least prominent malalignment, while the upper subgroup represented those with the most prominent malalignment. Three-dimensional motion analysis was used to obtain kinematic data.

68 57 Specific kinematic descriptors examined were joint angle at initial contact, peak angle, time-to-peak, or total joint angle change. Pearson s bivariate correlations were calculated to examine relationships between each alignment measure and the kinematic measures in the sagittal, frontal, and transverse planes. Multivariate analyses of variance were performed to compare each subgroup with the kinematic measures in each of the 3 tasks. Results: Many of the alignments were correlated with certain kinematic descriptors, however, it was difficult to predict the trend for each specific kinematic descriptor. We observed that the degree of femoral anteversion significantly affected hip kinematics and that this was regardless of gender. Tibial varum was significantly correlated with the greatest number of kinematic descriptors, however, the range in tibial varum measures was not large enough to display differences in kinematics for the extremes of alignment. Conclusions: Lower extremity alignment does appear to affect the kinematics of functional tasks, however, the amount of contribution of each alignment is relatively small. A majority of the significant correlations were relatively small with most alignments explaining less than 30% of the variance of any of the kinematic measures. In the case of femoral anteversion, there are differences in landing strategies that appear to be, in part related to that alignment which demonstrates that there is a relationship between some lower extremity alignments and the kinematics of functional tasks. These lower extremity alignments are those that are often demonstrated by fes and are also thought to influence the kinematics increasing the risk of knee injury. Future research should focus on the identification of risk factors for knee injury that may be demonstrated by s or fes.

69 58 INTRODUCTION There is a discrepancy between s and fes in regards to lower extremity injury rates Several intrinsic and extrinsic factors have been examined in order to explain this discrepancy. No specific difference has been identified to explain all contribution to the greater incidence of lower extremity injuries in fes. Two of these factors are lower extremity static alignments 4, 5, 7, 8, 30, 32, 35, , 17, and lower extremity kinematics. 19, 20, 26, 28, 64, 69, 70, 72 It is common knowledge that s and fes tend to display different normative values in lower extremity alignments. Of the measurable lower extremity alignments, fes tend to demonstrate larger q-angles, more genu recurvatum, femoral anteversion, and pelvic tilt, as compared to s. 41 There has been considerable discussion about lower extremity alignments and how they may relate to gender and injury. The differences in lower extremity alignments are one of the many factors that are studied to help explain the discrepancy in injury rates between s and fes. It is theorized that alignment will affect lower kinematics and that extremes of alignment may increase risk of injury by increasing the range of motion and thus the moments that act on a particular joint, and that ligaments may be abnormally stressed. Abnormal forces imparted on the joint may lead to overuse injuries or predispose an individual to acute injury. It is also of concern that there will be abnormal contact pressures within the joint, a theorized predisposition for osteoarthritis. Of concern to the clinician are the implications of malalignments to causation of injury. While lower extremity

70 59 malalignments do not always directly contribute to pathology, a connection is often drawn between the malalignment and the condition of interest, there is a potential relationship between static malalignments and overuse injuries. Kinematic performance between s and fes is one of the extrinsic factors that have been examined to explain, in part, the discrepancy in injury rates between the genders. It has been reported that fes tend to demonstrate more hip adduction, more knee valgus, and a stiffer landing compared to s. These kinematic are all theorized 16, 17, 19, 26, 28, 64, 72 to be predisposing factors for injury. Though demonstrated with several studies, the cause of the kinematic differences between genders is unknown. While there is information regarding the difference between the genders and kinematics, there is only speculation as to the influence on those kinematic differences and it is unknown if it is gender or the specific alignments that are typically displayed by the genders contribute to these differences. Examining novel, but sport-related, functional tasks may shed light on the specifics of kinematic differences. The purpose of this study is to examine the relationship between the magnitude of lower extremity alignment with the performance of three functional, sport-related tasks. An analysis of the relationships between a series of commonly measured lower extremity alignments and the kinematics at the hip and knee for 3 functional tasks was performed. Specific kinematic variables examined were joint angle at initial contact, peak angle, time-to-peak, and total joint angle change. A second analysis examined how the extremes of alignment may compare to more normal

71 60 measures in regards to 3D kinematics during functional tasks. It was hypothesized that there will be significant correlations between certain alignments and certain kinematics will exist and that trends between alignment and kinematics performance will exist. There will be a significant correlation between alignments that tend to be associated with fes and the kinematics that are typically described as more typical of fe movement patterns. It is also hypothesized that by making a comparison of the groups in extremes of alignment will reveal differences in task performance between these groups. Extremes of lower extremity alignment will contribute more to alterations in lower extremity kinematics than alignment values within the normative confidence intervals. Significant trends that are observed in the correlational analysis will be revealed as there will be a significant difference between groups with the least and most malalignment as compared to groups with a more normal alignment. METHODS Subjects Twenty-four healthy, active subjects (12 s; height = ± 7.5 cm; weight = 83.8 ± 17.6 kg and 12 fes; height = ± 5.7 cm; weight = 61.6 ± 6.3 kg) volunteered for participation in this study. Inclusion criteria required that each subject be between the ages of 18-30, with at least 1 year of competitive participation in the sport of basketball. Exclusion criteria required that each subject had no reported history of serious knee injury, and was free from any acute orthopedic injury to the back or lower extremity for at least 1 month prior to testing. It was also required that subjects never participated in any type of ACL injury prevention program or are currently participating in general

72 61 plyometric training. Subjects who met the inclusion and exclusion criteria were asked to participate. The subjects who agreed received and signed an informed consent, which was approved by the Institutional Review Board of the University of Virginia for use in this study. Lower Extremity Alignment Data Collection Six common measures of lower extremity posture were collected using previously established methods. Measures were performed on the subject s right lower extremity only. NAVICULAR DROP Navicular drop was determined using methods described by Bonci 10 and measured with a vernier height gauge (Mitutoyo America Corporation, Aurora, Il). The central point of the navicular tuberosity was located and marked. An initial measurement was taken with the subject seated, with both feet on the floor, unweighted and in subtalar neutral. The unweighted navicular position was the distance from the floor to the marked point on the navicular tuberosity. The subject then stood, keeping equal pressure on both feet and the measurement was repeated. Navicular drop was calculated as the difference between the two measurements. This method has been reported to have an intrarater reliability of.78 to Figure 1 demonstrates the methods for measuring navicular drop.

73 62 TIBIAL VARUM Tibial varum was determined as described by Tomaro 4, with the subject in a weightbearing, double-limb stance and equal weight on each foot. The posterior aspect of the shank was bisected two-thirds of the length of the tibia from the medial joint line to the medial malleolus. A second point was marked at the point bisecting the widest point from the medial malleolus to the lateral malleolus. Tibial varum is the angle at which the distal third of the tibia diverges from the perpendicular as measured with a standard goniometer. 4 The goniometer was modified with addition of a fluid level to improve the accuracy of measurement for this study. This measurement was taken without controlling for subtalar neutral. By not controlling for subtalar neutral, the position of the foot in relation to the shank is more functional. The interrater reliability has been reported as high as ICC=.83 with sufficient practice by the clinician. 3 Figure 2 demonstrates the methods for measuring tibial varum. QUADRICEPS ANGLE Quadriceps angle (Q-angle) was measured as described in Tomisch et al. 12 With the subject in standing, the central point of the patella was located as a line running from the anterior superior iliac spine (ASIS) that bisects the patella. The central point of the tibial tuberosity was also located and a second line drawn from that point to bisect the patella. Q-angle was determined as the acute angle made by those lines. This measurement was performed in standing in order to record a more functional representation of Q-angle. Special care was taken to assure that the subject s quadriceps were in a relaxed position, as contraction of the quadriceps would affect the position of the patella Intratester

74 63 reliability for standing q-angle is reported as.75 in well-trained testers. 79 Figure 3 demonstrates the methods for measuring q-angle. GENU RECURVATUM Genu recurvatum is the angle of knee hyperextension created by the femur and the fibula in the sagittal plane. This measurement was performed as described by Trimble et al. 6 While in standing, each subject was asked to extend the knee as fully as possible. In some cases, subjects reached hyperextension. The measurement was performed using standard goniometer. This method has been reported to have an intrarater reliability of Figure 4 demonstrates the methods for measuring genu recurvatum. FEMORAL ANTEVERSION 10, 13 The measurement of femoral anteversion was performed as previously described. The greater trochanter of the femur was located by palpation while the subject lay prone. With the knee flexed, the hip was passively internally and externally rotated until the greater trochanter could be palpated at its most lateral point. Femoral anteversion was determined with a standard goniometer as the acute angle formed by the tibia and an imaginary vertical line. Comparison of this technique with intraoperative measurements by Ruwe et al 13, demonstrated this method to be superior to radiologic techniques for determining femoral anteversion in children about to undergo surgery at the hip. Figure 5 demonstrates the methods for measuring femoral anteversion.

75 64 PELVIC TILT Pelvic tilt was determined as described in Petrone 14 using a PALpation Meter (Performance Attainment Associates, St. Paul, MN). The anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) were located and marked. One arm of the PALMeter was placed on the each landmark. Pelvic tilt was measured as the degree of anterior tilt of the pelvis in the sagittal plane. This method has been reported to be highly reliable (ICC =.99). 15 Figure 6 demonstrates the methods for measuring pelvic tilt. All measurements were performed by the same investigator (JMM). Alignment data were recorded by hand and transferred to a spreadsheet. Functional tasks MAXIMAL VERTICAL JUMP Each subject performed 5 trials of a one foot take-off/ two-foot landing vertical jump with a two-arm reach for maximal height. Subjects were instructed to take one step with the right leg and takeoff from that same leg and land on both feet. Figure 7 demonstrates the performance of the maximal vertical jump. SIDESTEP CUT Each subject performed 5 trials of a sidestep cutting task. The subject was asked to perform this task within an approximate 10 x 5 m space. The subject approached the force plate from the left at a 45 o angle, planted and then performed a 90 o change of direction, leaving the force plate at 45 o towards the left. If the subject performed a crossover cut or rounded out the direction change, the trial was discarded and repeated.

76 65 Figure 8 demonstrates the performance of the sidestep cut. JUMP STOP Each subject performed 5 trials of a jump stop task. The subject was asked to start at one end of the runway. The subject sprinted forward to a predetermined spot on the force plate, at which point the subject came to an abrupt halt, planting on the right foot and changing directions 30 o to the left. The subject then shifted back to a two-foot stance and jumped straight up in the air. This task is similar to the motion basketball player would perform after receiving a pass and taking a jump shot. Figure 9 demonstrates the performance of the jump stop. Each subject was to allowed to practice tasks until comfortable with performing the tasks in a repeatable fashion. The subject then performed five trials of each of these functional, sport-related tasks. All tasks were performed barefoot. Kinematics for these tasks were recorded by three-dimensional optoelectric stereophotogrammetry for each attempt for this task. Five trials of each task were collected and averaged for a single representation of each task for each subject. If performance of any task was overtly altered because of force plate targeting, the trial was discarded and repeated. Kinematic Analysis Three dimensional motion analysis was used to capture lower extremity kinematic data. Kinematic data were collected using a passive, 8-camera, 3-D VICON motion analysis system (Oxford Metrics Ltd.; Oxford, UK). Camera calibration errors were all below 1.3

77 66 mm. Marker trajectories were sampled at a rate of 120 Hz and a 30-frame fill gap threshold was set to reconstruct lost markers. Marker trajectories were filtered through a low-pass Woltering digital filter with predicted MSE value of 30 and a cutoff frequency of 15Hz. Static reproducibility and wand visibility was above 60%. Kinematic data was synchronized with vertical ground reaction force-sensitive floor data as recorded by one of four imbedded force plates (Kistler Instrument Corp.; Winterthur, Switzerland and AMTI; Watertown MA) and was used to identify the time at initial contact with the ground with respect to task performance. Hip and knee joint centers for the right and left leg were reconstructed using the Plug-in- Gait modeler (VICON Oxford, UK Peak Performance Technologies, Inc, CO). Hip and knee joint angles for the right leg were calculated and included in the analysis. Neutral hip and knee alignment was defined as 0. Relative flexion, internal rotation, and adduction were subsequently denoted as positive, whereas extension, external rotation, and abduction were negative. Each subject was fitted with 16 retroreflective markers (14-mm diameter) at specific anatomical locations (see Figure 10). Three-dimensional optoelectric stereophotogrammetry was used to capture the kinematic characteristics for 5 successful trials of each task. Failed trials, which included improper task performance by the subject or a technological system error, were discarded and the trial was run again.

78 67 Statistical Analysis Bivariate correlational analyses were performed for each kinematic variable (angle at initial contact, peak angle, time-to-peak, and total angle change from initial contact to peak) to identify any relationship between the independent variable (6 alignment measures) and the 6 measures of kinematics at the hip and knee using Pearson product moment calculations. Separate bivariate correlations were run for each of the 3 functional tasks. Multivariate analysis of variance was used to compare individual alignment groups to individual joint kinematics for each of the 3 tasks. Group assignment for the independent variable (individual malalignment) was determined by dividing each into lower(1), middle(2), and upper(3) thirds. The lower group represented subjects with the least prominent of that particular malalignment. The upper group represented subjects with the most prominent of the specific malalignment measurement. Details of the thirds cutpoints for each lower extremity alignment are presented in Table [6]. Means and standard errors of the means for each kinematic variable were calculated. A MANOVA was performed to determine the effect of malalignment group on each dependent variable (individual joint angles and rotations of the hip and knee). The kinematics were divided into families of similar variables. The families were defined by the anatomic location (i.e. hip or knee) and type of kinematic descriptor (i.e. joint angle at initial contact, peak angle, time-to-peak, and total joint angle change). Refer to Appendix B, Table 10 for details of kinematic families. Separate 1x3 MANOVAs were performed to evaluate the effect of extremes of alignment on each family of kinematic variables. These were run

79 68 for each of the three tasks. Wilk s lambda was used to identify significant models. In the event of a significant MANOVA, individual 1x3 ANOVAs and Tukey post hoc tests were run to identify the specific significant differences. Means and standard errors of the means for each variable were calculated to specifically describe differences. All statistical analyses were conducted in SPSS 13.0 (SPSS for Windows, SPSS Science Inc, Chicago, Ill). An alpha level was set a priori at.05 to determine statistical significance in all analyses. RESULTS Alignment by Kinematic Correlations VERTICAL JUMP Several significant correlations were identified between malalignment and kinematic measures during the vertical jump task. There was a significant inverse relationship between q-angle and knee adduction at initial contact (r = -.42, P =.04). There was an inverse relationship between static alignment of tibial varum and peak knee adduction (r = -.42, P =.04). There was an inverse relationship between q-angle and knee adduction time-to-peak (r = -.45, P =.03). There were a significant relationship for both q-angle (r =.57, P =.005) and femoral anteversion (r =.42, P =.05) with peak hip adduction angles. As these alignment measures increased, there was in increase in peak hip adduction angles during the vertical jump task. For hip internal rotation time-to-peak, there was a significant relationship with pelvic tilt (r =.42, P =.05). Tibial varum significantly affected the change in knee and hip angles from initial contact to peak in the frontal plane. At the knee, tibial varum inversely affected the change in valgus knee

80 69 angles (r = -.57, P =.004). As tibial varum increased, total change in knee valgus decreased. At the hip however, the relationship was positive (r =.50, P =.02); as tibial varum increased, the total change in hip adduction angle also increased. There was also significant relationship between q-angle and hip adduction total angle change (r =.52, P =.01). As q-angle increased, total change in hip adduction increased. SIDESTEP CUT There was a significant relationship between q-angle and knee internal rotation at initial contact (r =.46, P =.03). For hip internal rotation, there was an inverse relationship with tibial varum (r = -.48, P =.02). As tibial varum angle increased, peak hip internal rotation decreased. Tibial varum was also inversely related to peak knee valgus angles (r = -.48, P =.02). As tibial varum increased, peak knee valgus angles decreased. There were significant relationship for both tibial varum (r =.51, P =.01) and q-angle (r =.53, P =.01) and peak knee internal rotation angles. As these alignment measures increased, there was in increase in peak angle for the sidestep cutting task. Tibial varum was inversely correlated with the total change in knee valgus angles from initial contact to peak (r = -.74, P <.001). As tibial varum increased, the total change in knee valgus angles decreased. There were no relationships seen between degree of lower extremity alignment and time-to-peak values during the sidestep cutting task. JUMP STOP There was a significant inverse relationship between q-angle and knee adduction angles at initial contact (r = -.55, P =.007). As q-angle measures increased, knee adduction in

81 70 the frontal plane decreased. Genu recurvatum was positively correlated with knee internal rotation angles at initial contact (r =.42, P =.05). As genu recurvatum increased knee internal rotation angles at initial contact increased. There were significant inverse correlations for both tibial varum (r = -.54, P =.008) and q-angle (r = -.42, P =.05) with peak knee valgus angles. As these alignment measures increased, there was in decrease in peak knee valgus angle for the jump stop task. Genu recurvatum was significantly correlated with total change in hip adduction angles (r =.41, P =.05). As the measure of genu recurvatum increased, total change in hip adduction angle increased. There was an inverse relationship between tibial varum and the total change in knee valgus angles (r = -.62, P =.002). As tibial varum increased, the change in knee valgus angle from initial contact to peak decreased. There were no relationships seen between degree of lower extremity alignment and time-to-peak values during the jump stop task. Details of significant correlations are presented in Table [7]. Comparison of the Extremes of Lower Extremity Alignment and Kinematics VERTICAL JUMP Results of the MANOVA revealed a significant linear model (P =.04) for the comparison of genu recurvatum and hip time-to-peak. There was a significant difference between individual groups of genu recurvatum and hip internal rotation time-to-peak (P =.02). Post hoc testing revealed that genu recurvatum Group 1 (least recurvatum) differed from Group 2 (middle recurvatum) for hip internal rotation time-to-peak (P =.021). The group

82 71 demonstrating the smallest measure of genu recurvatum reached peak hip internal rotation faster than the middle group of genu recurvatum. The comparison of femoral anteversion with total change in hip angles revealed a significant linear model (P =.002). Total change in angle for both hip flexion (P =.04) and hip adduction (P =.005) was different for Groups 2 (middle) and 3 (most) for femoral anteversion. The middle group for femoral anteversion achieved more total hip flexion than the group with the most amount of femoral anteversion. In contrast, the middle group demonstrated less total change in hip adduction as compared to the group with the greatest degree of femoral anteversion. No other significant models were seen in these analyses for the vertical jump task. SIDESTEP CUT Results of the MANOVA revealed a significant differences for the comparison of knee peak angle and genu recurvatum group status (P =.045). However, the individual 1 x 3 ANOVAs for the 3 joint planes did not emerge as significant. See Table [8] for the results of the nonsignificant 1x3 ANOVA results of this significant MANOVA. No other significant models were seen in these analyses for the sidestep cutting jump task. JUMP STOP The comparison of femoral anteversion with total change in hip angles revealed a significant linear model (P =.002). There was a significant difference between the middle group of femoral anteversion and the group with most amount of anteversion for

83 72 time-to-peak knee adduction (P =.04) and time-to-peak knee internal rotation (P =.05). Group 3 (most femoral anteversion) reached both knee adduction and knee internal rotation faster than Group 2 (middle amount femoral anteversion). Group 1 also reached peak knee flexion faster than Group 2, however, post-hoc comparisons were nonsignificant. Details of significant results are presented in Table [9]. No other significant models were seen in these analyses for the jump stop task. DISCUSSION The purpose of this study was to examine the relationship between the magnitude of lower extremity alignment with knee and hip kinematic measures during the performance of three functional tasks. The first analysis examined relationships between a series of commonly measured lower extremity alignments and the kinematics of 3 functional tasks. The second analysis was used to examine the how the extremes of alignment may compare to more normal measures in regards to 3D kinematics during functional tasks. It is common knowledge that s and fes tend to display different normative values in lower extremity alignments. While there is a breadth of information regarding the difference between the genders and kinematics, there is only speculation as to the influence on those kinematic differences and is unknown if it is gender or the specific alignments that are typically displayed by the genders contribute to these differences. Kinematic differences between s and fes are one of the factors that have been 16, 17, 19, examined to explain, in part, the discrepancy in injury rates between the genders. 20, 26, 28, 64, 69, 70, 72 Though demonstrated in these studies, the cause of the kinematic

84 73 differences between genders is unknown. Examining novel, but sport-related, functional tasks may shed light on the specifics of kinematic differences. This aspect of the study was performed to identify the role of specific alignments that alter movement patterns independent of gender effects. It is theorized that alignment will affect lower kinematics and that extremes of alignment may increase risk of injury by increasing the range of motion and thus the moments that act on a particular joint, and that ligaments may be abnormally stressed. It is also of concern that there will be abnormal contact pressures within the joint, a theorized predisposition for osteoarthritis. Of concern to the clinician are the implications of malalignments to causation of injury. Based on the results of this study, there is a potential relationship between static malalignments and overuse injuries. Overall statements While many of the alignments were correlated with certain kinematic descriptors, it was difficult to predict the trend for each specific kinematic descriptor. The vertical jump was the most successful of the tasks in detecting trends between lower extremity alignments and kinematics. Overall, tibial varum was correlated with the greatest number of kinematic descriptors. Interestingly, navicular drop was not significantly related to any kinematic variables in either analysis. While navicular drop has been used as a static measure of pronation 11, the measures of navicular drop did not demonstrate a relationship with any of the kinematics for any of the tasks.

85 74 Tibial varum was significantly and negatively correlated with peak knee adduction angles and total change in knee adduction angle for all three tasks. In contrast, the range of tibial varum for this study population was not large enough to detect any significant differences between the thirds of tibial varum in regards to those kinematics. Similarly, q-angle was negatively correlated with knee adduction angle at initial contact for both the vertical jump and the jump stop, but no differences were found between the thirds of alignment for this measure. It is likely that there was not enough power to detect the differences between the thirds of alignment groups, however, the relationship between tibial varum and q-angle with kinematic descriptors appears to exist, and with more subjects, these differences may be revealed. Vertical jump FEMORAL ANTEVERSION At landing, the joint angles change to aid the absorption of ground reaction forces. A diminished level of joint angle change may increase forces imparted within the joints and be a predisposition to injury. Fe collegiate athletes have demonstrated a stiffer and more erect landing posture at initial contact when compared to collegiate athletes. 16, 19 Accommodation of the ground reaction forces by increasing the valgus angle at the knee could be a predisposition for a knee injury. Although both groups in the one study 16 demonstrated similar vertical ground reaction forces and imposed forces absorbed at the knee, the more erect posture brings the knee closer to full extension and potentially, hyperextension. In the second study 19, this was true for both a single-leg landing and single-leg forward hop tasks.

86 75 For the vertical jump task, there were two significant differences between alignment groups in regards to total angle change at the hip in two planes. The middle femoral anteversion group achieved a greater change in hip flexion angle compared to the group with the most femoral anteversion. In contrast, the group with the most femoral anteversion went through a greater change in hip adduction compared to the middle femoral anteversion group. This was also demonstrated in the correlational analysis, with a positive correlation seen between femoral anteversion and peak hip adduction angle. This may demonstrate that joint motion throughout the body is performed to absorb forces, but the accommodation strategies appear to differ depending on the degree of lower extremity alignment of femoral anteversion. The accommodation strategy for landing from a vertical jump may not be specifically related to gender, rather related to lower extremity alignment. It has been reported that fes tend to go into less hip flexion and more hip adduction & internal rotation when 19, 72 landing. Fes also tend to demonstrate more femoral anteversion compared to s. In accordance with these two previous observations, we observed that subjects with more femoral anteversion reached less hip flexion and achieved more hip adduction as an accommodation strategy. How this differed from the previous explanations is that gender has been used as the defining feature, while the results of the present study demonstrate a relationship between one lower extremity alignment that is associated with gender, but the landing strategy occurs regardless of gender.

87 76 For time-to-peak kinematics, the middle groups of genu recurvatum and femoral anteversion demonstrated slower time-to-peaks than groups that were at the extremes of those measures. For the vertical jump, those with the least amount of genu recurvatum demonstrated faster time-to-peak than those in the middle group of genu recurvatum. OTHERS While there were significant individual correlations between the measures of tibial varum, q-angle, and pelvic tilt and certain kinematic descriptors for each of those alignments, there were not significant differences between the groups of thirds of alignment. The individual contributions of the degree of tibial varum, q-angle, or pelvic tilt may have not been large enough to display a significant difference in alignment thirds groups for those same kinematics descriptors. It appears that trends exist, however the population sample may not have demonstrated a large enough range in the lower extremity alignments of tibial varum, q-angle, or pelvic tilt to demonstrate those same trends within the groups of alignment. The groups may not have been large enough or variable enough to reveal these same trends. Sidestep cut While there were significant correlations between the tibial varum and q-angle with certain kinematics, there was no particular lower extremity group for tibial varum or q- angle that was significantly different from each other in regards to any kinematic descriptors. The contribution of tibial varum or q-angle was relatively small.

88 77 Jump stop While there were several correlational relationships between certain lower extremity alignments and the jump stop task kinematics, femoral anteversion was not one of these significant correlations. This was likely the result of the interaction between femoral anteversion thirds. For example, there was a difference in the relationship between femoral anteversion thirds and time-to-peak knee in knee adduction angle. The extremes of femoral anteversion (the lowest and highest degrees of femoral anteversion), displayed significantly faster knee adduction time-to-peak compared to the middle group. There was no difference between the lowest and highest groups in regards to that measure. It seems that there is an envelope of function within which the amount of femoral anteversion is independent of knee adduction time-to-peak, however, when alignment falls outside that interval, the kinematics of the knee change, regardless of the magnitude of malalignment. Middle group of femoral anteversion also displayed slower time-to-peak in knee internal rotation compared to the group that displayed the most femoral anteversion. Time-topeak is a measure that may capture kinematics that may predispose to injury. Shorter time-to-peak angle measures may indicate a greater amount of stress on joints in two ways. An accommodation strategies paradigm has been proposed to model the relationship between a stressor and the body s response to accommodate that stressor 43. The body s accommodation strategies are in place to help maintain system homeostasis and to prevent injury 43, 44 The preparatory contraction of periarticular muscles in response

89 78 to perturbation provides stability and control of joint moments to prevent collapse , 45 The purpose is to provide efficient neuromuscular control. There is a need for efficient neuromuscular control to create dynamic joint stiffness and protective stability. Electromechanical delay (EMD) is the total time it takes the electrical signal for contraction to reach the muscle and for the muscle to develop force. Shorter time-to-peak values may be detrimental to the joint because of the shorter time to reach a meaningful and protective contraction of the periarticular musculature before the joint reaches its peak angle. Without meaningful contraction of the muscles around the joint, the forces of the perturbation are absorbed fully in the static structures (ligaments, joint capsule, or articular cartilage) of the joint. Shorter time-to-peak may also affect the material properties of the articular connective tissue. Connective tissue is viscoelastic and therefore, its response to loading is ratedependent. When a load is applied, the tissue deforms to accommodate those forces. As the rate of loading increases, the tissue responds by becoming stiffer. This increased stiffness protects the joint by allowing less deformation to the structure, however, if external forces exceed the yield point, permanent damage to the connective tissue occurs. Shorter time-to-peak may affect the joint structures causing an increased stiffness, which will initially provide protection the structures, but will also shorten the time needed to reach the yield point where permanent damage occurs.

90 79 LIMITATIONS Lower extremity malalignments are often implicated in certain overuse injuries and they are often the first item addressed when treating these condition. Though often related to injury, it is important to note that excessive lower extremity malalignment is not necessarily a cause of injury. Individuals with any particular alignment may or may not suffer injury. Likewise, an individual may be develop an injury that is normally associated with malalignments and not exhibit any of these postural problems. Data collection for this study was performed on a healthy population with no lower extremity injuries. While lower extremity alignments may affect kinematics, in this healthy population, the kinematics do not appear to be pathological for this population, and we cannot conclude that the kinematics displayed by these groups actually contribute to injury in the general population. Three-dimensional motion analysis is commonly utilized for biomechanical studies, however, there is error associated with this type of analysis. 59 Motion analysis can be used to recreate the kinematics of a functional task in the three spatial dimensions, however, these three planes are not equal with respect to the degree of error that is recorded with the signal of interest. 61 While there is relative confidence in the sagittal plane, there is a relative confidence in the accuracy of results in the sagittal plane, the frontal and transverse plane are less so. 61 Since the markers are fixed to the skin and not rigidly to the skeletal system 59, soft tissue artifact is the main contributing source of error 61, 62 and is difficult to filter out as it is a result of human motion and carries a frequency that is equal to that which is of interest.

91 80 Though the tasks designed for this study are functional in nature, they were described to the subject in full before performance of the task, and therefore, fully anticipated and not spontaneous. There is a conflict between constraining the task in order to make it reproducible between subjects and allowing the subject to perform the task unimpeded. Pre-designed functional tasks are good for capturing motions similar to sport-related performance 51, however, the anticipated performance of functional tasks may not entirely represent the true performance of these tasks in a real-life situation. 78 CONCLUSIONS Lower extremity alignment does appear to affect the kinematics of functional tasks, however, the amount of contribution of each alignment is relatively small. Tibial varum was significantly correlated with the greatest number of kinematic descriptors, however, the range in tibial varum measures was not large enough to display differences in kinematics for the extremes of alignment. The analysis of tibial varum to knee adduction total angle change displayed a moderate contribution (r 2 =.55). A majority of the significant correlations were relatively small with most alignments explaining less than 30% of the variance of any of the kinematic measures. We observed that femoral anteversion significantly affected hip kinematics and that this was regardless of gender. Some correlational trends were confirmed when each lower extremity alignment was divided into thirds of least, middle, and greatest degree of alignment. There may not have been a wide enough range in alignment measures to

92 81 corroborate the trends seen for other kinematics. In the case of femoral anteversion, there are differences in landing strategies that appear to be, in part related to that alignment. This study demonstrated that there is a relationship between some lower extremity alignments and the kinematics of functional tasks. These lower extremity alignments are those that are often demonstrated by fes and are also thought to influence the kinematics increasing the risk of knee injury. Future research should focus on the identification of risk factors for knee injury that may be demonstrated by s or fes.

93 82 Table 6: Cutpoints for the Thirds of Lower Extremity Alignment Group 1: Least Group 2: Middle Group 3: Most Navicular Drop (cm) < > 1.3 Tibial Varum ( o ) < > 7.0 Q-angle ( o ) < > 14 Genu Recurvatum ( o ) < > 6 Pelvic Tilt ( o ) < > 11 Femoral Anteversion ( o ) < > 13

94 83 Table 7: Significant Correlations between Lower Extremity Alignments and Kinematics Alignment Correlated With: r R 2 P-value Vertical Jump Tibial Varum Peak Knee Adduction Angle Tibial Varum Hip Adduction Total Angle Change Tibial Varum Knee Adduction Total Angle Change Q Angle Knee Adduction at Initial Contact Q Angle Peak Hip Adduction Angle Q Angle Hip Adduction Total Angle Change Q Angle Time-to-Peak Knee Adduction Pelvic Tilt Time-to Peak Hip Internal Rotation Femoral Anteversion Peak Hip Adduction Angle Sidestep Cut Tibial Varum Peak Hip Internal Rotation Tibial Varum Peak Knee Adduction Angle Tibial Varum Peak Knee Internal Rotation Tibial Varum Knee Adduction Total Angle Change <.001 Q Angle Knee Internal Rotation at Initial Contact Q Angle Peak Knee Internal Rotation Jump Stop Tibial Varum Peak Knee Adduction Angle Tibial Varum Knee Adduction Total Angle Change Q Angle Knee Adduction at Initial Contact Q Angle Peak Knee Adduction Angle Genu Recurvatum Knee Internal Rotation at Initial Contact Genu Recurvatum Total Change Hip Adduction Angle

95 84 Table 8: Nonsignificant 1x3 ANOVA results of the significant general linear model comparing Genu Recurvatum and Peak Knee Angles during the sidestep cutting task (Mean ± SD) Group 1 (Least) Group 2 (Middle) Group 3 (Most) P-value GLM x 3 ANOVA Sig Peak Knee Flexion Angle ( o ) 53.8 ± ± ± Peak Knee Adduction Angle ( o ) ± ± ± Peak Knee Internal Rotation Angle ( o ) 22.4 ± ± ±

96 85 Table 9: Significant Relationships Between Extremes of Lower Extremity Alignment and Kinematics (Mean ± SD) Kinematics P-value 95% Confidence intervals Post Hoc Significance VERTICAL JUMP Genu Recurvatum Group Mean Time-to-Peak Hip Internal Rotation (s) 1 Least genu recurvatum 0.1 ± Middle genu recurvatum 0.2 ± , Femoral Anteversion Group Mean Angle Change Hip Flexion ( o ) 2 Middle femoral anteversion 39.5 ± Most femoral anteversion 23.9 ± , Mean Angle Change Hip Adduction ( o ) 2 Middle femoral anteversion 2.7 ± Most femoral anteversion 7.3 ± , JUMP STOP Femoral Anteversion Group Mean Time-to-Peak Knee Adduction (s) 1 Least femoral anteversion.11 ±.07 2 Middle femoral anteversion.21 ± , , Most femoral anteversion.11 ±.05 Mean Time-to-Peak Knee Internal Rotation (s) 2 Middle femoral anteversion.19 ±.09 3 Most femoral anteversion.10 ± ,.2.04

97 86 Chapter 5 CONCLUSIONS These studies were an attempt to identify specific lower extremity alignments that tend to be associated with gender and identify if these alignments affect lower extremity kinematics regardless of gender. The three kinematic descriptors that were significantly different were all directly related to the hip and are believed to increase stresses at the knee. It was concluded that while there were few kinematic descriptors that were significantly different between s and fes, how gender and kinematic performance are specifically related is unknown. The static alignments of navicular drop, tibial varum, q-angle, genu recurvatum, pelvic tilt, and femoral anteversion are commonly measured as part of a lower extremity examination. These 6 alignments have all been implicated for increasing the risk of certain acute injuries, in particular noncontact anterior cruciate ligament (ACL) injuries, and also chronic injuries to the lower extremity. The use of 3D motion analysis allowed for an examination of how clinical measures of alignment may relate to kinematic performance of 3 sport-related, functional tasks. Based on our statistical analysis, lower extremity alignment does appear to affect the kinematics of functional tasks, however, the amount of contribution of each alignment is relatively small and may only display a trend. A majority of the significant correlations were relatively small with most alignments explaining less than 30% of the variance of

98 87 any of the kinematic measures. While some correlational trends were confirmed when each lower extremity alignment was divided into thirds of least, middle, and greatest degree of alignment, there may not have been a wide enough range in alignment measures to corroborate the trends seen for other kinematics. Additional statistical evaluation such as analysis of covariance using alignment as the covariate or chi-square nonparametric statistical tests were not appropriate at this time because of the small sample size. Larger numbers would allow for appropriate use of those statistical tests and would potentially provide insight into gender-specific differences and the influence of alignment on kinematic behavior. This study demonstrated that there is a relationship between certain lower extremity alignments and the kinematics of functional tasks and that this association between lower extremity alignments that are generally associated with fes and kinematics that are implicated for knee injury. COMPARISON OF FINDINGS WITH RESEARCH HYPOTHESES Study 1: 1. The hypothesis that there will be a significant difference between genders in regards to the lower extremity alignments of q-angle, genu recurvatum, and femoral anteversion was supported. It was observed that fes demonstrated larger measures for all three of these alignments. Though it was expected that fes would demonstrated a greater degree of pelvic tilt, it was not supported by this study. Based on previous studies, there will most likely be a difference between genders for q-angle, genu recurvatum, pelvic tilt, and femoral anteversion.

99 88 2. The hypothesis that there will be a significant difference between s and fes in regards to certain lower extremity kinematics was supported, in that fes tended to perform these functional tasks using landing accommodation strategies at the hip that place a greater degree of stress on the knee in the frontal and transverse planes when compared to s. In contrast, it was not observed in this study that fes landed with a more erect, stiffer landing as hypothesized. Study 2: 3. The hypothesis that there will be significant correlations between certain lower extremity alignments and certain lower extremity kinematics was supported. Several alignments were significantly associated with kinematic descriptors. The specific alignments that tend to be greater in fes (q-angle, genu recurvatum, femoral anteversion, anterior pelvic tilt) were related to movement patterns that are often implicated as being more typical of fe movement patterns and predispositions to injury, however, these were independent of gender. 4. The hypothesis that extremes of lower extremity alignment will contribute more to alterations in lower extremity kinematics than alignment values within the normative values was supported, for there were significant differences between groups with the least and most malalignment as compared to groups with a more normal alignment. Though these relationships were observed, few of the

100 89 significant trends that were observed in the correlational analysis demonstrated a significant difference between groups. It was probable that the range of alignment values was not large enough to demonstrate significant differences between groups. CLINICAL IMPLICATIONS Lower extremity alignment does contribute to alterations in kinematics. The kinematics that are altered based on lower extremity alignment tend to be altered towards imparting more stress on the knee. There are certain lower extremity alignments that more fes tend to demonstrate (larger q-angles, more genu recurvatum, and greater femoral anteversion) and these alignments are one of the many factors associated with the increase in knee injury rates for fes. More importantly, some s may also demonstrate these same alignments and are equally susceptible to knee injury. Of importance to the clinician is identifying individuals who are at an increased risk of knee injury and focusing on reducing the risk of injury. FUTURE RESEARCH Future research should focus on the identification of risk factors for knee injury that may be demonstrated by s or fes. Rather than examining gender specific differences, research should target on the identification of the specific causes of the differences in movement patterns between s and fes rather than implicating gender alone. By identifying specific risk factors, new prevention strategies can be developed and refined, with the goal of reducing the risk of injury to all individuals.

101 90 References 1. Riegger-Krugh C, Keysor JJ. Skeletal malalignments of the lower quarter: correlated and compensatory motions and postures. J Orthop Sports Phys Ther. 1996;23(2): McPoil TG, Schuit D, Knecht HG. A comparison of three positions used to evaluate tibial varum. J Am Podiatr Med Assoc. 1988;78(1): Lohmann KN, Rayhel HE, Schneiderwind WP, Danoff JV. Static measurement of tibia vara. Reliability and effect of lower extremity position. Phys Ther. 1987;67(2): Tomaro J. Measurement of tibiofibular varum in subjects with unilateral overuse symptoms. J Orthop Sports Phys Ther. 1995;21(2): Tillman MD, Bauer JA, Cauraugh JH, Trimble MH. Differences in lower extremity alignment between s and fes. Potential predisposing factors for knee injury. J Sports Med Phys Fitness. 2005;45(3): Trimble MH, Bishop MD, Buckley BD, Fields LC, Rozea GD. The relationship between clinical measurements of lower extremity posture and tibial translation. Clin Biomech (Bristol, Avon). 2002;17(4): Hertel J DJ, Braham RA. Lower extremity malalignments and anterior cruciate ligament injury history. J Sports Sci & Med. 2004;3(4): Krivickas LS. Anatomical factors associated with overuse sports injuries. Sports Med. 1997;24(2): Gross MT. Lower quarter screening for skeletal malalignment--suggestions for orthotics and shoewear. J Orthop Sports Phys Ther. 1995;21(6): Bonci CM. Assessment and evaluation of predisposing factors to anterior cruciate ligament injury. J Athl Train. 1999;34(2): Mueller MJ, Host JV, Norton BJ. Navicular drop as a composite measure of excessive pronation. J Am Podiatr Med Assoc. 1993;83(4): Tomsich DA, Nitz AJ, Threlkeld AJ, Shapiro R. Patellofemoral alignment: reliability. J Orthop Sports Phys Ther. 1996;23(3): Ruwe PA, Gage JR, Ozonoff MB, DeLuca PA. Clinical determination of femoral anteversion. A comparison with established techniques. J Bone Joint Surg Am. 1992;74(6): Petrone MR, Guinn J, Reddin A, Sutlive TG, Flynn TW, Garber MP. The accuracy of the Palpation Meter (PALM) for measuring pelvic crest height difference and leg length discrepancy. J Orthop Sports Phys Ther. 2003;33(6): Krawiec CJ, Denegar CR, Hertel J, Salvaterra GF, Buckley WE. Static innominate asymmetry and leg length discrepancy in asymptomatic collegiate athletes. Man Ther. 2003;8(4): Decker MJ, Torry MR, Wyland DJ, Sterett WI, Richard Steadman J. Gender differences in lower extremity kinematics, kinetics and energy absorption during landing. Clin Biomech (Bristol, Avon). 2003;18(7):

102 17. Ford KR, Myer GD, Toms HE, Hewett TE. Gender differences in the kinematics of unanticipated cutting in young athletes. Med Sci Sports Exerc. 2005;37(1): Quatman CE, Ford KR, Myer GD, Hewett TE. Maturation Leads to Gender Differences in Landing Force and Vertical Jump Performance: A Longitudinal Study. Am J Sports Med Lephart SM, Ferris CM, Riemann BL, Myers JB, Fu FH. Gender differences in strength and lower extremity kinematics during landing. Clin Orthop Relat Res. 2002(401): McLean SG, Walker KB, van den Bogert AJ. Effect of gender on lower extremity kinematics during rapid direction changes: an integrated analysis of three sports movements. J Sci Med Sport. 2005;8(4): Hewett TE. Neuromuscular and hormonal factors associated with knee injuries in fe athletes. Strategies for intervention. Sports Med. 2000;29(5): Hewett TE, Myer GD, Ford KR. Decrease in neuromuscular control about the knee with maturation in fe athletes. J Bone Joint Surg Am. 2004;86- A(8): Hewett TE, Stroupe AL, Nance TA, Noyes FR. Plyometric training in fe athletes. Decreased impact forces and increased hamstring torques. Am J Sports Med. 1996;24(6): Huston LJ, Wojtys EM. Neuromuscular performance characteristics in elite fe athletes. Am J Sports Med. 1996;24(4): Shultz SJ, Perrin DH. Using surface electromyography to assess sex differences in neuromuscular response characteristics. J Athl Train. 1999;34(2): Ferber R, Davis IM, Williams DS, 3rd. Gender differences in lower extremity mechanics during running. Clin Biomech (Bristol, Avon). 2003;18(4): Zazulak BT, Ponce PL, Straub SJ, Medvecky MJ, Avedisian L, Hewett TE. Gender comparison of hip muscle activity during single-leg landing. J Orthop Sports Phys Ther. 2005;35(5): Ford KR, Myer GD, Hewett TE. Valgus knee motion during landing in high school fe and basketball players. Med Sci Sports Exerc. 2003;35(10): Hewett TE, Myer GD, Ford KR, Heidt RS, Jr., Colosimo AJ, McLean SG, van den Bogert AJ, Paterno MV, Succop P. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in fe athletes: a prospective study. Am J Sports Med. 2005;33(4): Taunton JE, McKenzie DC, Clement DB. The role of biomechanics in the epidemiology of injuries. Sports Med. 1988;6(2): Picciano AM, Rowlands MS, Worrell T. Reliability of open and closed kinetic chain subtalar joint neutral positions and navicular drop test. J Orthop Sports Phys Ther. 1993;18(4): Mizuno Y, Kumagai M, Mattessich SM, Elias JJ, Ramrattan N, Cosgarea AJ, Chao EY. Q-angle influences tibiofemoral and patellofemoral kinematics. J Orthop Res. 2001;19(5):

103 33. Norwood LA, Jr., Cross MJ. The intercondylar shelf and the anterior cruciate ligament. Am J Sports Med. 1977;5(4): Arendt EA, Agel J, Dick R. Anterior cruciate ligament injury patterns among collegiate men and women. Journal of athletic training. 1999;34(2): Loudon JK, Jenkins W, Loudon KL. The relationship between static posture and ACL injury in fe athletes. J Orthop Sports Phys Ther. 1996;24(2): Nyland J, Kuzemchek S, Parks M, Caborn DN. Femoral anteversion influences vastus medialis and gluteus medius EMG amplitude: composite hip abductor EMG amplitude ratios during isometric combined hip abduction-external rotation. J Electromyogr Kinesiol. 2004;14(2): Witvrouw E, Werner S, Mikkelsen C, Van Tiggelen D, Vanden Berghe L, Cerulli G, Mascal CL, Landel R, Powers C. Clinical classification of patellofemoral pain syndrome: guidelines for non-operative treatment. Knee Surg Sports Traumatol Arthrosc. 2005;13(2): Mascal CL, Landel R, Powers C. Management of patellofemoral pain targeting hip, pelvis, and trunk muscle function: 2 case reports. J Orthop Sports Phys Ther. 2003;33(11): Hillstrom HJ, Brower DJ, Whitney K, McGuire J, Schumacher HR. Lower extremity conservative realignment therapies for knee osteoarthritis. Physical Medicine and Rehabilitation: State of the Art Reviews. 2002;16(3): Hunter DJ, Zhang Y, Niu J, Tu X, Amin S, Goggins J, Lavalley M, Guermazi A, Gale D, Felson DT. Structural factors associated with malalignment in knee osteoarthritis: the Boston osteoarthritis knee study. J Rheumatol. 2005;32(11): Medina JM Hertel J, Braham RA. Correlations between lower extremity malalignments in collegiate athletes. (unpublished data). 42. Kelso M, Medina JM, Hertel J. Correlations between lower extremity malalignments and medial tibial stress syndrome. (unpublished data). 43. James CR, Bates BT, Dufek JS. Classification and comparison of biomechanical response strategies for accommodating landing impact. J Appl Biomech. 2003;19(2): Riemann BL, Lephart SM. The sensorimotor system. Part I. The physiologic basis of functional joint stability. J Athl Train. 2002;37(1): Loeb GE GC. Principles of Neural Science. 4 ed. New York: McGraw-Hill Companies, Inc; Riemann BL, Lephart SM. The sensorimotor system. Part II. The role of proprioception in motor control and functional joint stability. J Athl Train. 2002;37(1): Horita T, Komi PV, Nicol C, Kyrolainen H. Interaction between pre-landing activities and stiffness regulation of the knee joint musculoskeletal system in the drop jump: implications to performance. Eur J Appl Physiol. 2002;88(1-2): Solomonow M, Baratta R, Zhou BH, D'Ambrosia R. Electromyogram coactivation patterns of the elbow antagonist muscles during slow isokinetic movement. Exp Neurol. 1988;100(3):

104 49. Baratta R, Solomonow M, Zhou BH, Letson D, Chuinard R, D'Ambrosia R. Muscular coactivation: the role of the antagonist musculature in maintaining knee stability. Am J Sports Med. 1988;16(2): Riemann BL, Myers JB, Lephart SM. Sensorimotor system measurement techniques. J Athl Train. 2002;37(1): Croce RV, Russell PJ, Swartz EE, Decoster LC. Knee muscular response strategies differ by developmental level but not gender during jump landing. Electromyogr Clin Neurophysiol. 2004;44(6): Hewett TE, Stroupe AL, Nance TA, Noyes FR. Plyometric training in fe athletes. Decreased impact forces and increased hamstring torques. Am J Sports Med. 1996;24(6): Shultz SJ, Perrin DH, Adams JM, Arnold BL, Gansneder BM, Granata KP. Neuromuscular response characteristics in men and women after knee perturbation in single-leg, weight-bearing stance. J Athl Train. 2001;36(1): Huston LJ, Wojtys EM. Neuromuscular performance characteristics in elite fe athletes. Am J Sports Med. 1996;24(4): Trontelj JV. Muscle fiber conduction velocity changes with length. Muscle Nerve. 1993;16(5): Bell DG, Jacobs I. Electro-mechanical response times and rate of force development in s and fes. Med Sci Sports Exerc. 1986;18(1): Cappozzo A, Della Croce U, Leardini A, Chiari L. Human movement analysis using stereophotogrammetry. Part 1: theoretical background. Gait Posture. 2005;21(2): Della Croce U, Leardini A, Chiari L, Cappozzo A. Human movement analysis using stereophotogrammetry. Part 4: assessment of anatomical landmark misplacement and its effects on joint kinematics. Gait Posture. 2005;21(2): Chiari L, Della Croce U, Leardini A, Cappozzo A. Human movement analysis using stereophotogrammetry. Part 2: instrumental errors. Gait Posture. 2005;21(2): Durlach NI MA, eds. Virtual reality: scientific and technological challenges Leardini A, Chiari L, Della Croce U, Cappozzo A. Human movement analysis using stereophotogrammetry. Part 3. Soft tissue artifact assessment and compensation. Gait Posture. 2005;21(2): Andriacchi TP, Alexander EJ. Studies of human locomotion: past, present and future. J Biomech. 2000;33(10): Cappozzo A, Catani F, Croce UD, Leardini A. Position and orientation in space of bones during movement: anatomical frame definition and determination. Clin Biomech (Bristol, Avon). 1995;10(4): McLean SG, Huang X, van den Bogert AJ. Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury. Clin Biomech (Bristol, Avon). 2005;20(8): Myer GD, Ford KR, McLean SG, Hewett TE. The Effects of Plyometric Versus Dynamic Stabilization and Balance Training on Lower Extremity Biomechanics. Am J Sports Med

105 66. McLean SG, Walker K, Ford KR, Myer GD, Hewett TE, van den Bogert AJ. Evaluation of a two dimensional analysis method as a screening and evaluation tool for anterior cruciate ligament injury. Br J Sports Med. 2005;39(6): Besier TF, Lloyd DG, Cochrane JL, Ackland TR. External loading of the knee joint during running and cutting maneuvers. Med Sci Sports Exerc. 2001;33(7): Nyland J, Caborn DN, Shapiro R, Johnson DL, Fang H. Hamstring extensibility and transverse plane knee control relationship in athletic women. Knee Surg Sports Traumatol Arthrosc. 1999;7(4): McLean SG, Lipfert SW, van den Bogert AJ. Effect of gender and defensive opponent on the biomechanics of sidestep cutting. Med Sci Sports Exerc. 2004;36(6): McLean SG, Neal RJ, Myers PT, Walters MR. Knee joint kinematics during the sidestep cutting maneuver: potential for injury in women. Med Sci Sports Exerc. 1999;31(7): Coury HJ, Brasileiro JS, Salvini TF, Poletto PR, Carnaz L, Hansson GA. Change in knee kinematics during gait after eccentric isokinetic training for quadriceps in subjects submitted to anterior cruciate ligament reconstruction. Gait Posture Ford KR, Myer GD, Smith RL, Vianello RM, Seiwert SL, Hewett TE. A comparison of dynamic coronal plane excursion between matched and fe athletes when performing single leg landings. Clin Biomech (Bristol, Avon). 2006;21(1): Boden BP, Dean GS, Feagin JA, Jr., Garrett WE, Jr. Mechanisms of anterior cruciate ligament injury. Orthopedics. 2000;23(6): Ireland ML. Anterior cruciate ligament injury in fe athletes: epidemiology. J Athl Train. 1999;34(2): Myer GD, Ford KR, Palumbo JP, Hewett TE. Neuromuscular training improves performance and lower-extremity biomechanics in fe athletes. J Strength Cond Res. 2005;19(1): Hass CJ, Schick EA, Tillman MD, Chow JW, Brunt D, Cauraugh JH. Knee biomechanics during landings: comparison of pre- and postpubescent fes. Med Sci Sports Exerc. 2005;37(1): Yu B, Stuart MJ, Kienbacher T, Growney ES, An KN. Valgus-varus motion of the knee in normal level walking and stair climbing. Clin Biomech (Bristol, Avon). 1997;12(5): Besier TF, Lloyd DG, Ackland TR, Cochrane JL. Anticipatory effects on knee joint loading during running and cutting maneuvers. Med Sci Sports Exerc. 2001;33(7): Shultz SJ, Nguyen AD, Windley TC, Kulas AS, Botic TL, Beynnon BD. Intratester and intertester reliability of clinical measures of lower extremity anatomic characteristics: implications for multicenter studies. Clin J Sport Med. 2006;16(2): Medvecky MJ, Bosco J, Sherman OH. Gender disparity of anterior cruciate ligament injury. Etiological theories in the fe athlete. Bull Hosp Jt Dis. 2000;59(4):

106 81. Oliphant JG, Drawbert JP. Gender Differences in Anterior Cruciate Ligament Injury Rates in Wisconsin Intercollegiate Basketball. J Athl Train. 1996;31(3): Agel J, Arendt EA, Bershadsky B. Anterior cruciate ligament injury in national collegiate athletic association basketball and soccer: a 13-year review. Am J Sports Med. 2005;33(4): Bell NS, Mangione TW, Hemenway D, Amoroso PJ, Jones BH. High injury rates among fe army trainees: a function of gender? Am J Prev Med. 2000;18(3 Suppl): Bennell KL, Brukner PD. Epidemiology and site specificity of stress fractures. Clin Sports Med. 1997;16(2): Hewett TE, Myer GD, Ford KR. Anterior cruciate ligament injuries in fe athletes: Part 1, mechanisms and risk factors. Am J Sports Med. 2006;34(2): Wilder RP, Sethi S. Overuse injuries: tendinopathies, stress fractures, compartment syndrome, and shin splints. Clin Sports Med. 2004;23(1):55-81, vi. 87. Tomaro JE, Burdett RG, Chadran AM. Subtalar joint motion and the relationship to lower extremity overuse injuries. J Am Podiatr Med Assoc. 1996;86(9): Tomaro JE, Butterfield SL. Biomechanical treatment of traumatic foot and ankle injuries with the use of foot orthotics. J Orthop Sports Phys Ther. 1995;21(6): Hreljac A, Marshall RN, Hume PA. Evaluation of lower extremity overuse injury potential in runners. Med Sci Sports Exerc. 2000;32(9):

107 96 APPENDIX A: ADDITIONAL METHODS Figure 1: Measurement of Navicular Drop Figure 2: Measurement of Tibial Varum

108 97 Figure 3: Measurement of Quadriceps Angle Figure 4: Measurement of Genu Recurvatum

109 98 Figure 5: Measurement of Femoral Anteversion Figure 6: Measurement of Pelvic Tilt

110 99 Figure 7: Vertical Jump Figure 8: Sidestep Cut Figure 9: Jump Stop

111 100 Figure 10: Retroreflective Marker Placement 16 Markers/8 per side 2nd metatarsal head Lateral malleolus Calcaneus (same level as 2nd met head) Midshank (in-line with knee lateral joint line and lateral malleolus) Lateral joint line Mid-thigh (in-line with lateral joint line and greater trochanter) Anterior superior iliac spine Posterior superior iliac spine

112 101 APPENDIX B: DATA TABLES Table 3: Gender Comparison of All Lower Extremity Kinematics for the Vertical Jump HIP X Initial Contact HIP Y Initial Contact HIP Z Initial Contact KNEE X Initial Contact KNEE Y Initial Contact KNEE Z Initial Contact HIP X Peak angle HIP Y Peak angle HIP Z Peak angle KNEE X Peak angle KNEE Y Peak angle KNEE Z Peak angle HIP X TTP HIP Y TTP HIP Z TTP KNEE X TTP KNEE Y TTP KNEE Z TTP HipDX HipDY HipDZ KneeDX KneeDY KneeDZ fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe N Std. Mean Deviation Sig

113 102 Table 4: Gender Comparison of All Lower Extremity Kinematics for the Sidestep Cut HIP X Initial Contact HIP Y Initial Contact HIP Z Initial Contact KNEE X Initial Contact KNEE Y Initial Contact KNEE Z Initial Contact HIP X Peak angle HIP Y Peak angle HIP Z Peak angle KNEE X Peak angle KNEE Y Peak angle KNEE Z Peak angle HIP X TTP HIP Y TTP HIP Z TTP KNEE X TTP KNEE Y TTP KNEE Z TTP HipDX HipDY HipDZ KneeDX KneeDY KneeDZ fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe N Std. Mean Deviation Sig

114 103 Table 5: Gender Comparison of All Lower Extremity Kinematics for the Jump Stop HIP X Initial Contact HIP Y Initial Contact HIP Z Initial Contact KNEE X Initial Contact KNEE Y Initial Contact KNEE Z Initial Contact HIP X Peak angle HIP Y Peak angle HIP Z Peak angle KNEE X Peak angle KNEE Y Peak angle KNEE Z Peak angle HIP X TTP HIP Y TTP HIP Z TTP KNEE X TTP KNEE Y TTP KNEE Z TTP HipDX HipDY HipDZ KneeDX KneeDY KneeDZ fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe N Std. Mean Deviation Sig

115 104 Table 10: Families of Similar Kinematic Variables HIP INITIAL CONTACT FAMILY HIP X Initial Contact HIP Y Initial Contact HIP Z Initial Contact KNEE INITIAL CONTACT FAMILY KNEE X Initial Contact KNEE Y Initial Contact KNEE Z Initial Contact HIP PEAK ANGLE FAMILY HIP X Peak angle HIP Y Peak angle HIP Z Peak angle KNEE PEAK ANGLE FAMILY KNEE X Peak angle KNEE Y Peak angle KNEE Z Peak angle HIP TIME-TO-PEAK ANGLE FAMILY HIP X TTP HIP Y TTP HIP Z TTP KNEE TIME-TO-PEAK ANGLE FAMILY KNEE X TTP KNEE Y TTP KNEE Z TTP HIP TOTAL ANGLE CHANGE FAMILY HipDX HipDY HipDZ KNEE TOTAL ANGLE CHANGE FAMILY KneeDX KneeDY KneeDZ

116 105 APPENDIX C: INFORMED CONSENT Page 1 of 3 Project Title: Correlations between lower extremity malalignments, neuromuscular recruitment patterns, and kinematics during selected movements Please read this consent agreement carefully before you decide to participate in the study. Purpose of the research study: The purpose of this study is to look at the relationships between lower body alignments, muscle activity of the hip, thigh, and leg muscles, and motion during movements typically seen in sports. What you will do in the study: Your height, weight, age, and gender will be recorded. Six surface measurements of alignment will be taken on each leg. After these measurements, small areas on the skin where self-adhering electrode pads will be placed will be shaved and cleaned with rubbing alcohol. These electrode pads are for recording muscular activity. The electrode pads will be applied. Cable wires will be attached from the pads to a machine that measures muscular activity. Small reflective markers will also be attached to certain landmarks on each of your legs. A special camera reads these markers and records the specific motions during the tasks you will perform. You will then be asked to warm-up on a stationary bicycle. You will then be informed of how to perform each task, and then be allowed to practice until the task pattern is understood and repeatable. You will have data about the activity in his/her thigh muscles collected by the machine during five trials of 3 selected tasks. The tasks include a jump for maximal vertical height (taking one step and jumping straight up), a zig-zag cutting pattern, and the jump-stop (cutting forward, stopping quickly, pivoting 30 o, and then jumping). Time required: You will spend about 2 hours in each session. The total experiment will require about 2 hours. Risks: There is a slight risk of muscle or joint injury with uncontrolled actions. The tasks involved in this study are active in nature, which is the reason for using subjects who are healthy and active. Risk of injury will be reduced by clearing the testing area of any obstructions. Risk of injury will also be reduced by making sure that you fully understand each task before to each trial. You must be in good health and free from current injuries that prevent normal movement. If you have a history of ACL injury and/or reconstruction will be excluded from the study. There is a possibility of allergic reaction from the electrodes, which may include redness or irritation.

117 106 Page 2 of 3 Benefits: There are no direct benefits to you for participating in this research study. The study may help us understand the relationship between lower extremity structure and muscular and movement patterns during sports-related tasks. Confidentiality: The information that you give in the study will be handled confidentially. Your information will be assigned a code number. The list connecting your name to this code will be kept in a locked file. When the study is completed and the data have been analyzed, this list will be destroyed. Your name will not be used in any report. You will be recorded by video camera, however, this camera only records the markers on your skin. You cannot be identified by your video analysis. However, all video recordings will be erased at the completion of this project. Voluntary participation: Your participation in the study is completely voluntary. Right to withdraw from the study: You have the right to withdraw from the study at any time without penalty. If you choose to withdraw before completion of the study all your data and any of your video analysis will be destroyed. How to withdraw from the study: If you want to withdraw from the study, tell the investigator and quietly leave the room. There is no penalty for withdrawing at any time. Payment: You will receive no payment for participating in the study. What happens if you are hurt during this study? You will not be paid for lost wages, disability, or discomfort if you suffer any unexpected injury directly resulting from this study. Treatment for an unexpected injury directly resulting from the research study that is not covered by the sponsor or your insurance will be provided free of charge at the University of Virginia. You should talk to the study researcher if you have questions about being paid for an unexpected injury caused by this study. You do not give up legal rights for personal injury by signing this form.

118 107 Page 3 of 3 If you have questions about the study, contact: Primary Investigator: Jennifer Medina, MS, ATC, CSCS Department of Sports Medicine/Athletic Training 226 Memorial Gymnasium University of Virginia Charlottesville, VA Telephone: (434) office (814) cell Faculty Advisor: Jay Hertel, PhD, ATC Department of Sports Medicine/Athletic Training 209 Memorial Gymnasium University of Virginia Charlottesville, VA Telephone: (434) office If you have questions about your rights in the study, contact: Luke Kelly, Chairman, Institutional Review Board for the Social and Behavioral Sciences, 400 Ray C. Hunt Drive, Suite 360, Room 4, University of Virginia, P.O. Box , Charlottesville, VA Telephone: (434) Agreement: You must be 18 years of age or older to consent to participate in this research study. If you consent to participate in this research study and to the terms above, please sign your name and indicate the date below. I agree to participate in the research study described above. Participant s Signature: Date: For investigator s completion: I, the undersigned, verify that the above informed consent procedure has been followed. Investigator s Signature: Date: You will receive a copy of this form for your record.

119 APPENDIX D: PLUG-IN-GAIT FORM 108