Analysis of a Modified Active Knee Extension Test

Transcription

1 Analysis of a Modified Active Knee Extension Test Yvonne Kane, MS, PT' lay Bernasconi, MS, PT2 P hysical therapists frequently assess hamstring muscle length (HML) in patients with hamstring injuries, patellofemoral problems, and lumbosacral dysfunctions. These assessments influence treatment, return to previous activity, and prediction of susceptibility to injury. Hamstring injuries have a high rate of occurrence and reoccurrence in the athletic population (1, 8, 14). Eecreased hamstring flexibility, inadequate rehabilitation, and premature return to a sport are believed to be causative factors in predisposing an athlete to hamstring injury (1, 5, 8, 14). Physical therapists should use the most sensitive test to assess decreased hamstring length. In assessment of patients with lumbosacral or knee dysfunction, a skilled clinician performs a number of selected tests to isolate specific structures that may be the cause of abnormal biomechanical alignment. These include the sit-andreach and toe-touch tests, which have been criticized as providing only a gross indication of HML (5, 10, 14). Both tests involve vertebral flexion, anterior pelvic rotation, hip flexion, knee extension, and ankle dorsiflexion as well as a stretch on the surrounding musculature and fascia. Kippers and Parker studied trunk and hip flexion in a toe-touch test and correlated it to finger-floor distance (12). Conversely, the Hamstring injuries occur and reoccur at high rates in the athletic population. The purpose of this study was to describe the effect of contralateral hip flexion on pelvic rotation in the sagittal plane and ipsilateral active knee extension during a modified active knee extension test. Twentyseven normal subjects were tested, yielding 54 sets of data. Active knee extension was performed in five positions of contralateral hip flexion and was videotaped. Measurements of pelvic and knee joint angles were obtained from the film. The results indicated the least amount of pelvic rotation was 5.5" which occurred at maximum contralateral hip flexion. Analysis of variance revealed a difference between test positions that was statistically significant for pelvic rotation and knee extension (p <.05). Pelvic rotation can be effectively controlled during an active knee extension test by maximally flexing the contralateral hip. The active knee extension test can be used as an accurate assessment tool to evaluate hamstring muscle length. Key Words: straight leg raising, flexibility, angular measurement ' Assistant professor and clinical coordinator, faculty practice and program, University of Medicine and Dentistry of New lersey and Medical Center of Princeton, Nl President, furnace Brook Physical Therapy, Quincy, MA When this study was conducted, the authors were pursuing Master of Science degrees in physical therapy, orthopaedic and sports medicine, at the MCH Institute of Health Professions, Boston, MA. straight leg raise (2-4, 6, 13) and active knee extension (AKE) (7, 15) tests allow posterior pelvic motion to occur. A wide variety of factors could be responsible for decreased flexibility (9, 11). These may include age, sex, period of immobilization, and the presence of muscle pathology. Therefore, an alternative method of testing should be considered to determine if a more isolated measure of HML is possible. The passive straight leg raise (PSLR) test is an additional test used frequently to indicate HML. Previous studies have recognized the occurrence of pelvic motion in utilizing this test (2, 13). Stabilization of the pelvis is recommended, but the method used to stabilize the pelvis is not described. In a study where the pelvis was stabilized, Medeiros reported that the mean range of the pretest pelvifemoral angles was between 96.9 and 89.9" (1 3). Bohannon examined pelvic rnotion in the PSLR test using cinematographic analysis (2). Three groups were tested, each with different variations of stabilization with or without straps across the contralateral leg and anterior pelvis, by measuring the angle of the pelvis to the horizontal, the angle of SLR to the pelvis, and the angle of SLR to the horizontal. The mean, maximum increase in pelvic rotation from a resting position was found to be 24.9". He concluded that despite stabilization techniques, the SLR test failed to accurately measure HML JOSPT Volume 15 Number 3 March 1992

2 METHODS due to the occurrence of pelvic rotation. Medeiros and Bohannon state that if the SLR in relation to the pelvis is measured, the SLR test can be used to measure HML (2, 13). However, their marking and measuring system has limited application in the clinic. A follow-up study on the influence of pelvic and lower limb motion in the PSLR test revealed that posterior pelvic rotation occurred early in the PSLR, and the contribution of rotation increased as the angle of the SLR to the horizontal increased (3). Bohannon also looked at the relationship of pelvis and thigh motion during unilateral and bilateral hip flexion (4). Pelvic motion was reported to be similar whether hip flexion was performed actively or passively, but it was greater bilaterally than unilaterally. Bohannon concluded that more pelvic rotation occurred in the PSLR test than in hip flexion with knee flexion. In a study on the reliability of the AKE test, Gadjosik and Lusin attempted to stabilize each subject with straps across the contralateral thigh and anterior superior iliac spine (ASIS) (7). A cross wire on a metal frame to maintain thigh position, an end point of knee extension, a pendulum goniometer, and skin markings were used to improve reliability. The authors stated that pelvic rotation was minimized but did not quantify this motion. The AKE test appears to offer the most accurate measure of HML. Positioning the subject in posterior pelvic rotation should minimize the amount of pelvic motion during testing. The investigators expected that as the contralateral hip was flexed, less pelvic motion would occur during active knee extension. Accurate testing of HML would require that the occurrence of pelvic rotation be eliminated or minimized. The objective of this study was to determine whether the AKE, as a measure of HML, can be improved to eliminate pelvic motion in a sagittal plane. The purpose of the study was to describe the influence of contralateral hip flexion on pelvic rotation in a sagittal plane and ipsilateral knee extension range of motion when a subject is performing an AKE. METHOD Subjects This descriptive study was performed on normal men and women aged years. The sample consisted of 27 subjects and yielded 54 sets of data (Table 1). Participants were excluded from the study if there was a history of hip or knee internal derangement of if they manifested any type of hamstring injury or orthopaedic Dr neurological disor- All pelvic and knee measurements were made directly from the videotape. der of the lumbar spine, pelvis, or lower extremities at the time of testing. Subjects in the study participated voluntarily. Prior to testing, each subject was given an oral review of the testing procedures and a consent form, which was read and signed. A release for the educational use of the - videotaped test session was also obtained. Pretest Procedures Each test was videotaped using a Panasonic Digital 5000 video camera with zoom lens (Panasonic Company, Division of Matsushita Electric Corporation of American, One Panasonic Way, Secaucus, NJ 07094; zoom lens with auto iris, F 1.6 Model WV-LV ). The camera was relayed to a Panasonic recorder (Model #8950) and Panasonic television monitor (Model #I30 1 M, QSI Systems, Field Frane Counter, Woburn, MA). An external frame counter was added since the recorder had freeze-frame capabilities for data analysis. The camera lens was placed 65 inches from the mid-thigh of every subject's tested limb. The lens aperture was standardized for each subject, and the camera was kept level to the floor for each test session. Standardized instructions were given to each subject. Both investigators were present for every test session. Each subject was placed supine on a Cybex Upper Body Exercise Table (UBXT) (Cybex, Division of Lumbex, Inc., Ronkonkoma, NY), which was aligned perpendicular to a Cybex dynamometer (Figure 1). The right, lower extremity was tested first. A foot rest was attached to the table for the contralateral foot. The lateral malleolus and a point two inches superior to the fibula head were marked with a surgical skin pen. All marks were clearly made Contralateral Pelvic Angle with PelViC Angle at Pelvic Angle Active Knee Hip Position Knee Resting Knee Difference Extension Extension Resting 72.6 (12.6) 82.2 (13.7) 9.6 (3.5) (9.1) 45' 74.5 (12.3) 83.4 (13.5) 8.9 (3.5) (7.8) 90' 74.9 (12.7) 84.9 (14.2) 10.1 (3.9) (8.1) 120' 78.0 (12.5) 85.9 (13.3) 7.9 (3.5) (7.2) Maximal Flexion 81.4 (11.7) 86.9 (12.9) 5.5 (3.3) (6.2) TABLE 1. Summary of results (x SD). - Volume 15 Number 3 March 1992 JOSPT

3 The subjects were instructed to attempt maximum knee extension on each test and to complete this motion within three seconds. Timing was established with a metronome. By maintaining a hand on the contralateral ASIS, the investigator could detect and note the presence of any extraneous pelvic motion in a coronal or frontal plane that occurred during AKE. Upon completion of one AKE in each of the five test positions, the left lower extremity was tested using the same procedure. FIGURE 1. Jest position one, modified Active Knee EJ rtension Test. and heavily outlined to improve visualization needed for data analysis from the videotape (see Figure 1). These skin markings were adapted from Mundale et al (1 4). A long arm input adaptor with thigh pad was then attached to the Cybex dynamometer. The subject's right hip was flexed to 90". Finally, the subject's ASIS and posterior superior iliac spine (PSIS) were identified by palpation by an investigator. While one investigator maintained contact with these points, the second investigator drew a line between the two points with the skin pencil, using a flexible ruler. Any clothing that would interfere with visualization of this line was taped back. A pillow was provided for the subject's head. The subjects were instructed to maintain their hands on their abdomen, except during test position five. Testing The AKE test was carried out while placing the subject's contralatera1 hip in each of five angles of flexion. Test position one was a supine, resting "neutral" position on the subject's contralateral leg on the UBXT. Test positions two, three, and four were 45,90 and 120" of contralateral hip flexion, respec- tively. Test position five was maximum, passive hip flexion when the subjects pulled the leg with their hands to achieve the range of motion. The order of testing was rotated among subjects using a standardized sequence: 12345, , ,345 12, Once the With the exception of position three, there was a progressive decrease in the amount of pelvic motion as the contralateral hip was flexed. contralateral hip was positioned, an investigator palpated both ASIS and visually checked the pelvic alignment in a coronal and frontal plane. The investigator maintained one hand lightly on the contralateral ASIS as the subject was asked to actively extend the right knee with the right foot positioned in plantar flexion. Measurement All pelvic and knee measurements were made directly from the videotape. The reliability of this method was highly accurate and was established in a pilot study. Each set of measurements was taken independently by both investigators to determine interrater reliability. Joint angles that required alignment to the horizontal, such as contralateral hip flexion or pelvic position, were measured with a modified goniometer. A standard level was attached to the stationary arm of this goniometer in an effort to improve the reliability of the measurement. A descrip tion of the angles measured can be found in the legend for Figure 2. RESULTS The means, standard deviations, and ranges for all pelvic and knee measurements by test position are presented in Table 1. This table illustrates that, with the exception of position three, there was a progressive decrease in the amount of pelvic motion as the contralateral hip was flexed. The least amount of pelvic motion (5.5") occurred in position five. With the exception of position three, the active knee extension angle was found to progressively in- JOSPT * Volume 15 * Number 3 * March 1992

4 -A GREATER TROCHANTER - PSIS FIGURE 2. Measurements in the Modified Active Knee Extension Test, position one. Angle A depicts the measurement of the pelvis at resting and at maximum knee extension. The resting pelvic angle was defined as the angle taken when the videotape was frozen two frames before knee extension was observed to begin. The measurement of the pelvis at maximum knee extension was defined as the position of the pelvis in the frame that was used for recording maximum knee extension. Angle B is the maximum angle of active knee extension. ASIS-anterior superior iliac spine; PSIS-posterior superior iliac spine. crease as the contralateral hip was flexed. Analysis of Pelvic Rotation A two-way analysis of variance of test positions and knee side revealed significant main effects (F4, 260 = 14.31, p < 0.001) for test position, but not for side (Table 1). A subsequent Scheffe's post hoc test for differences among means revealed that test position five had significantly less (p < 0.05) pelvic motion than positions one, two, three, and four. The means for positions one, two, three, and four did not significantly differ from each other. There were also significant differences (p < 0.05) in pelvic motion by sex, with women showing less motion by about 2" in every test position. However, a two-way analysis of covariance, adjusting for sex, did not diminish the significance of the effects of position. Analysis of Knee Extension A two-way analysis of covariance revealed significant differences (F4.260 = 4.59, P < 0.002) in knee extension for test position, and post hoc analysis indicated that extension in position five was significantly greater than positions one, two, and three (p < 0.05). with position four being intermediate. In knee extension, there was also a significant difference (F1.260 = 7.27, p < 0.008) for right versus left extremity. The left extremity had consistently less knee extension by 1-4". Again, while there were differences (p < 0.0 1) in extension for males versus females, these did not affect the significance of the test position. As an initial step in investigating the relationship between pelvic and knee motions, the correlation between the difference in pelvic rotation and knee extension based on comparative values for test positions one and five was analyzed. A Pearson correlation coefficient was used. A weak, negative correlation was found for this relationship (r = ). Intertester reliability between both investigators was tested for all pelvic and knee measurements. A Pearson correlation coefficient of r = 0.97 was found for all pelvic measurements, and a correlation coefficient of r = 0.94 was found for all knee extension measurements. Finally, extraneous pelvic motion in either a coronal or frontal plane occurred 10 times in 54 tests. Of those 10, five were noted at position three. However, no extraneous pelvic motion was noted to occur in either test position one or five. DISCUSSION The authors expected that as the contralateral hip was flexed, less pelvic motion would occur during active knee extension. In analysis of pelvic motion, position five is shown to be significantly different from any other test position, in addition to having the least amount of pelvic motion. This would suggest that position five is the best test position. The pelvis displayed the most amount of posterior pelvic rotation and extraneous motion when the contralateral hip was flexed to 90" (position three). The leg, as a long lever acting to stabilize the pelvis (position one), and the stabilization offered through approximation of the contralateral thigh in position five were negated in 90" of hip flexion. Thus, only the surrounding musculature was available to support the pelvis during AKE. The results confirmed that the greatest variability and least control of the pelvis occurred at 90" of hip flexion (position three), suggesting that position three is a poor test position. Because the amount of pelvic motion in any test position was less Volume 15 Number 3 March 1992 JOSPT

5 than that reported by Bohannon in his analysis of the SLR, the modified AKE test is a more accurate test of HML. Bohannon suggests that the amount of pelvic rotation can be accounted for through additional measurement of the pelvifemoral angle and stabilization. However, the time required for this measurement and his suggested method of stabilization make this impractical in a clinical setting. Females were reported to have less pelvic motion and greater knee extension than males. This supports the clinical observation that women have greater hamstring flexibility than males. It is also important to consider the implications on the sacroiliac joint. Females have more anterior torsion due to the effect of the center of gravity in standing. Greater flexibility of the hamstring muscle could increase inherent instability and possibly lead to greater risk of sacroiliac conditions. Men with decreased flexibility may experience increased displacement of the pelvis or ilium in injuries involving full hamstring stretch. By rotating the pelvis posteriorly, the origin of the hamstring muscle is brought closer to its insertion; thus, AKE was expected to increase. This was confirmed by results shown in Table 1. If test position five differed from one, two, and three, the clinician should use one test position. Since differences exist between right and left knee extension measurements, it is not practical to compare both sides. This raises the question as to whether a correlation exists between an extremity with less AKE and the injured side. The investigators anticipated that a negative correlation would occur between pelvic motion and knee extension. However, the weak correlation value of r = suggests that pelvic rotation may not be the only factor that influences knee extension in the AKE test. This relationship is poorly understood. One explanation for the weak correlation is that the 90" hip flexion position of the tested leg places the pelvis in some posterior rotation. Therefore, the amount of additional posterior rotation that can occur during the test may be too small to significantly affect the larger range of knee extension. The high degree of reliability found between investigators is not of great significance to the clinician. The methods used for measurement were not appropriate for a clinical setting. A limitation of this study was the use of a single camera. An additional camera could have documented and quantified any pelvic motion in the coronal or frontal plane that occurred during the knee extension tests. Suggestions for future studies include: I) further investigation of the relationship of pelvic rotation to AKE, 2) examination of another type of stabili~ation technique for the tested leg instead of the isokinetic device that provided the high degree of reliability in measurement, and 3) the establishment of a value for desirable knee extension based on the functional requirements of the individual, which could include participation in a specific sport, 4) determining normative values for knee extension in test position five, and 5) investigation of possible correlations between the less flexible extremity and the involved side. CONCLUSION The AKE test, as described in this study, can be used as an accurate tool for the assessment of HML when the clinician wishes to minimize pelvic motion, such as in the rehabilitation of a competitive sprinter. Consistent positioning of the contralateral hip is important for repeated measures; however, the least amount of pelvic motion occurred when the contralateral hip was placed in maximum flexion. The effects of pelvic rotation on the measurement of knee extension when assessing HML in an AKE test may be of limited importance. JOSPT ACKNOWLEDGMENTS We wish to thank the MGH Physical Therapy Department for the use of equipment and space to perform our testing and data collection; our readers, Nancy Watts, PhD, PT and Claire McCarthy, PT, MGH; and our statistician, Mary Hediger, University of Medicine and Dentistry of New Jersey. REFERENCES Agre I: Hamstring injuries: Proposed aerological factors, prevention, and treatment. Sports Med 2:2 1-33, 1985 Bohannon RW: Cinematographic analysis of the passive straight leg raise test for hamstring muscle length. Phys Ther 62: , 1982 Bohannon RW, Cadjosik RL, LeVeau BF: Contribution of pelvic and lower limb motion to increases in the angle ofpassive straight leg raising. Phys Ther 65: , Bohannon RW, Cadjosik RL, LeVeau BF: Relationship of pelvic and thigh motions during unilateral and bilateral hip flexion. Phys Ther 65: 1 SO , 1985 Coole WC, Cieck lh: An analysis of hamstring strain and their rehabilitation. I Orthop Sports Phys Ther 9:77-85, 1987 Cadjosik R L, Bohannon R W: Clinical measurement of range of motion: Review of goniometry emphasizing reliability. Phys Ther 67: , 1987 Cadjosik RL, Lusin C: Hamstring muscle thickness: Reliability of an activeknee-extension test. Phys Ther 63: , 1983 Garrett WE, Califf IC, Basset FH: Histochemical correlates of hamstring injuries. Am ) Sports med 12:98-102, 1984 Curewitsch A, O'Neil M: Flexibility of healthy children. 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6 flexibility in young females. Res Q 57: , Kendall HL, Kendall F: Normal flexibility according to age groups. I Bone loint Surg 30A: , Kippers V, Parker A: Toe touch test: A measure of its validity. Phys Ther 67: , Medeiros I, Smidt G, Burmeister L, Soderberg G: Influence of isometric exercise and passive stretch on the hip joint motion. Phys Ther 57: , Mundale M, Hislop H, Kottke F: Evaluation of extension of the hip. Arch Phys Med Rehabil37:75-80, Sutton G: Hamstrung by hamstring strains: A review of the literature. I Orthop Sports Phys Ther 5: , Tangiawa MC: Comparison of the hold-relax procedure and passive mobilization on increasing muscle. Phys Ther 52: , Volume 15 Number 3 March 1992 JOSPT