Sonographic Evaluation of the Iliotibial Band at the Lateral Femoral Epicondyle

Transcription

1 ORIGINAL RESEARCH Sonographic Evaluation of the Iliotibial Band at the Lateral Femoral Epicondyle Does the Iliotibial Band Move? Elena J. Jelsing, MD, Jonathan T. Finnoff, DO, Andrea L. Cheville, MD, Bruce A. Levy, MD, Jay Smith, MD Videos online at Received June 22, 2012, from the Departments of Physical Medicine and Rehabilitation (E.J.J., A.L.C., J.S.), Orthopedic Surgery (B.A.L.), and Radiology (J.S.), Mayo Clinic College of Medicine, and Mayo Clinic Sports Medicine Center (B.A.L., J.S.), Rochester, Minnesota USA; and Tahoe Orthopedics and Sports Medicine, South Lake Tahoe, California USA (J.T.F.). Revision requested August 6, Revised manuscript accepted for publication November 13, Address correspondence to Jay Smith, MD, Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine, 200 First St SW, 14th Floor, Rochester, MN USA. Abbreviations ITB, iliotibial band; ITBS, iliotibial band syndrome; LFE, lateral femoral epicondyle doi: /ultra Objectives The purpose of this study was to determine whether the iliotibial band (ITB) moves relative to the lateral femoral epicondyle (LFE) as a function of knee flexion in both non weight-bearing and weight-bearing positions in asymptomatic recreational runners. Methods Five male and 15 female asymptomatic recreational runners (10 30 miles/wk) aged 18 to 40 years were examined with sonography to assess the distance between the anterior fibers of the ITB and the LFE in full extension, 30 of knee flexion, and 45 of knee flexion. Measurements were obtained on both knees in the supine (non weight-bearing) and standing (weight-bearing) positions. Results The distance between the anterior fibers of the ITB and the LFE decreased significantly from full extension to 45 of knee flexion in both supine (0.38-cm average decrease; P <.001) and standing (0.71-cm average decrease; P <.001) positions. These changes reflect posterior translation of the ITB during the 0 to 45 flexion arc of motion in both the supine and standing positions. Conclusions Sonographic evaluation of the ITB in our study population clearly revealed anteroposterior motion of the ITB relative to the LFE during knee flexionextension. Our results indicate that the ITB does in fact move relative to the femur during the functional ranges of knee motion. Future investigations examining ITB motion in symptomatic populations may provide further insight into the pathophysiologic mechanisms of ITB syndrome and facilitate the development of more effective treatment strategies. Key Words iliotibial band; iliotibial band syndrome; sonography I liotibial band syndrome (ITBS) is one of the most common causes of lateral knee pain among athletes and active populations, affecting up to 12% of runners at some point during their careers. 1,2 Patients typically present with activity-related deep achy lateral knee pain at the level of the lateral femoral epicondyle (LFE) that is worse during the initial 25 to 30 of knee flexion. 1 3 Although multiple risk factors have been associated with the development of ITBS, overuse during running and jumping activities appears to be the primary etiologic factor in most cases. 1,2,4 Refractory symptoms may result in the need for surgical intervention, permanent alteration of activities, or both. 1,2, by the American Institute of Ultrasound in Medicine J Ultrasound Med 2013; 32:

2 Despite the high prevalence of ITBS, its precise pathoetiology remains a topic of debate. Traditionally, it was believed that the iliotibial band (ITB) translated over the LFE during the initial 25 to 30 of knee flexion, potentially irritating the ITB or its associated bursa during repetitive activities such as running. 2 6,8 15 This injury model adequately explained the predilection for ITBS among runners, the production of maximal symptoms between 25 and 35 of knee flexion, the physical examination finding of tenderness at the posterior ITB, and a positive Noble compression test result. 1 4 However, Fairclough and colleagues 14,15 questioned the previously held notion that the ITB translates with respect to the LFE during knee flexion-extension. Instead, they reported that reciprocal tightening of the anterior and posterior portions of the ITB during knee flexion-extension creates the illusion of motion. 14,15 In addition, they observed a small degree of medio lateral motion of the ITB and therefore concluded that ITBS is not a friction syndrome but a result of entheseal traction and cyclic compression of the neurovascular rich fatty tissue located between the ITB and distal femur just proximal to the LFE. 14,15 Developing a more complete and accurate understanding of ITB function at the LFE is a necessary prerequisite to optimize prevention and treatment strategies for ITBS. Although sonography has been used to characterize static structural changes in patients presenting with ITBS as well as dimension changes during ITB stretching, no prior research using sonography has evaluated the motion of the ITB in symptomatic or asymptomatic populations. 8,9,16 23 The purpose of this study was to use sonography to determine the position of the ITB relative to the LFE as a function of knee flexion in both non weightbearing and weight-bearing positions in asymptomatic recreational runners. It was hypothesized that sonographic evaluation of the ITB would reveal posterior translation of the anterior fibers of the ITB relative to the LFE. Materials and Methods Participants This study was approved by the Institutional Review Board of the corresponding author s institution. Twenty male and female asymptomatic recreational runners were recruited by and flyers at a local fitness center. All healthy 18- to 40-year-old men and women who ran between 10 and 30 miles/wk and did not have a previous diagnosis of ITBS in either knee were eligible to participate. Exclusion criteria were applied to both lower limbs and included a history of lower limb fractures or surgery; a history of low back, gluteal, hip, or knee pain that required attention by medical personnel during the past year; and a history of knee pain requiring activity modification or medical treatment. Informed consent was obtained from all participants, and remuneration was provided for participation. Each participant s age, height, weight, calculated body mass index, and running experience (miles per week and years as a runner) were recorded. Bilateral Ober testing was performed to document any substantial ITB tightness. To perform this test, the participant was side lying with the bottom knee flexed to flatten the lumbar spine. The examiner stabilized the pelvis and passively flexed the top hip and knee to 90. The hip was then passively abducted and extended to place the ITB in tension. The examiner then allowed the knee to slowly drop by gravity until it reached its final resting angle. 21 If the knee dropped to or past neutral (parallel to the examination table), then a negative test result was recorded. Sonographic Examination Each participant underwent bilateral ITB sonographic examinations performed by the senior investigator (J.S.) using an iu22 ultrasound machine with an L12-5 linear array transducer (Philips Healthcare, Bothell, WA). At the time of the investigation, the senior investigator had more than 7 years of experience in diagnostic and interventional musculoskeletal sonography, including evaluation of the lateral knee region. With the participant in a supine position and the right knee fully extended, the ITB was identified by palpation cephalad to the LFE, and the transducer was placed transversely over the ITB, providing a short-axis view of the ITB fibers (Figure 1). Cephalocaudad scanning in both long and short axes was then performed to identify the anterior fibers of the ITB at the level of the continuous bony contour of the LFE. At this point, the transducer was placed short axis to the ITB and the distance (centimeters) between the anterior ITB fibers and the peak of the bony contour of the LFE was measured with the electronic digital calipers on the ultrasound machine (Figure 2). Positive measurements indicated that the anterior aspect of the ITB was anterior to the LFE, whereas negative values were used to indicate that the anterior ITB fibers were posterior to the LFE. The ITB-to-LFE distance was measured once with the participant supine and the knee fully extended and then repeated at 30 and 45 of knee flexion, as determined with an electrogoniometer (Acumar ACU002 digital inclinometer; Lafayette Instrument Co, Lafayette, IN). This process was then repeated on the left knee J Ultrasound Med 2013; 32:

3 After supine measurements, each participant then stood on the examination table in a double-leg position to repeat the measurement in a weight-bearing position. To avoid fatigue, the participants started in 30 of knee flexion, then rested in full extension, and finally progressed to 45 of knee flexion. An electrogoniometer was again used to obtain the correct flexion angles in these weight-bearing positions. The distance between the anterior-most fibers of the ITB and the bony contour of the LFE was again recorded at 30, 0 (full extension), and 45 of knee flexion in these weight-bearing positions (Figure 3). Measurements were first obtained on the left knee, and then the process was repeated on the right knee. Pilot testing revealed that the posterior fibers of the ITB were more challenging to identify than the anterior Figure 1. The transducer is positioned transversely on the LFE to obtain a short-axis view of the iliotibial band in the following positions: A, full extension in the supine position; B, 45 of knee flexion in the supine position; C, full extension in the standing position; and D, 45 of knee flexion in the standing position. A B C D J Ultrasound Med 2013; 32:

4 A Figure 2. Sonographic view with the transducer positioned transversely on the LFE to obtain a short-axis view of the iliotibial band in the supine position. A, Calipers measuring the ITB (anterior fibers)-to-lfe distance with the knee in full extension. B, Calipers measuring the ITB (anterior fibers)- LFE distance with the knee in 45 of knee flexion. Bottom is deep (medial); left, anterior (ANT); right, posterior; and top, superficial (lateral). LG indicates lateral gastrocnemius. B fibers in some participants because the posterior fibers blended almost imperceptibly with the fascia posteriorly. However, despite the difficulties in identifying the posterior fibers in some participants, we thought it important to study both the anterior and posterior fiber relationships in a subset of our study group to determine whether the posterior fibers also moved relative to the LFE with flexion. Therefore, we examined both the anterior and posterior fibers in a volunteer subset of our study group who had sonographically identifiable anterior and posterior margins. In this subset of 4 participants, the distances from the posterior fibers of the ITB to the LFE were again recorded in supine and standing positions at 0, 30, and 45 of knee flexion, in both knees (Figure 4). Statistics Descriptive statistics were calculated for the study population using means and proportions for continuous and binary variables, respectively. Twelve measurements were obtained for each participant, representing the distance between the anterior (all 20 participants) or posterior fibers (subset of 4 participants) of the ITB and the bony contour of the LFE (0, 30, and 45 flexion, both supine and standing, on both lower limbs), yielding highly correlated data. Skew and kurtosis testing were performed on these measurements to assess normality. Linear regression analyses, adjusted for within-subject correlation, were used to evaluate differences in the anterior ITB-to-LFE measurements when participants knees were flexed versus extended and when participants were supine versus standing. Because 7 comparisons were performed, the Bonferroni correction was used, and α =.007 was considered statistically significant. A preliminary analysis suggested that there were no sex-related or left-right leg differences; thus, we combined both sides of all 20 participants for this analysis. All statistical analyses were performed with Stata version 11.0 software for Windows (StataCorp, College Station, TX). Figure 3. Sonographic view with the transducer positioned transversely on the LFE to obtain a short-axis view of the iliotibial band in the standing position. A, Calipers measuring the ITB (anterior fibers)-to-lfe distance with the knee in full extension. B, Calipers measuring the ITB (anterior fibers)- to-lfe distance with the knee in 45 of knee flexion. Bottom is deep (medial); left, posterior; right, anterior (ANT); and top, superficial (lateral). LG indicates lateral gastrocnemius. A B 1202 J Ultrasound Med 2013; 32:

5 A B Figure 4. Sonographic view with the transducer positioned transversely on the LFE to obtain a short-axis view of the iliotibial band in the supine position. A, Calipers measuring the ITB (posterior fibers)-to-lfe distance with the knee in full extension. B, Calipers measuring the ITB (posterior fibers)-to-lfe distance with the knee in 45 of knee flexion. Bottom is deep (medial); left, anterior (ANT); right, posterior; and top, superficial (lateral). LG indicates lateral gastrocnemius. Results Demographics of the Participants The study population consisted of 5 men and 15 women with a mean age ± SD of 27 ± 3.7 years (range, years) and a mean body mass index of 23 ± 2.7 kg/m 2 (range, kg/m 2 ) who had been running a mean of 17 ± 7.1 miles/wk (range, miles/wk) for a mean of 8 ± 6.1 years (range, 1 26 years). Ober test results were negative for all participants. Movement of the ITB During Flexion The distance from the anterior fibers of the ITB to the apex of the LFE decreased from the fully extended to 30 and the fully extended to 45 positions in both the supine (non weight-bearing) and standing (weight-bearing) positions, reflecting posterior movement of the ITB relative to the LFE (Table 1). The change was significant for the following motion arcs: 0 to 45 in the supine position (0.38-cm average decrease), 0 to 30 in the standing position (0.33-cm average decrease), and 0 to 45 in the standing position (0.71-cm average decrease). As stated in Materials and Methods, a subset of 4 participants (3 women and 1 man) with easily identifiable posterior ITB margins also had their posterior ITB-to-LFE distance measurements recorded in the same study positions (0, 30, and 45 of knee flexion in both the supine and standing positions). The distance from the posterior fibers of the ITB to the apex of the LFE increased from the fully extended to 45 positions in both the supine (non weight-bearing) and standing (weight-bearing) positions, reflecting posterior movement of the posterior ITB relative to the LFE (Table 2). The change in these distances was significant for the following motion arcs: 0 to 45 in the supine position, 0 to 30 in the standing position, and 0 to 45 in the standing position. These changes paralleled the anterior ITB-to-LFE distance measurements. Differences Secondary to Weight-Bearing Status During standing at full extension, the anterior fibers of the ITB were on average cm more anterior to the apex of the LFE than during full extension in the supine position (Table 3). No significant differences were seen between the standing and supine positions at 30 and 45 of knee flexion. Discussion Although ITBS is common among runners, there is still debate over the pathoetiology of this condition. 2 4,12 15 Traditionally, clinicians believed that the ITB translated over the LFE during running, thus creating the potential for frictional irritation of the ITB or its underlying bursa. 2 5,8 12 More recently, Fairclough and colleagues 14,15 have challenged the notion that the ITB moves anteroposteriorly relative to the LFE. These researchers proposed that the soft tissue anchoring the ITB to the lateral femur would preclude substantial anteroposterior translatory ITB motion. They supported this hypothesis by observing that the ITB did not appear to move anteroposteriorly when visually inspecting a highly defined athlete s knee from the side during flexion-extension. Furthermore, they documented mediolateral ITB motion on magnetic resonance imaging of asymptomatic individuals during knee flexionextension and hypothesized that mediolateral ITB motion with cyclic compression of the underlying neurovascular fibrofatty tissue may be the a major pathoetiologic factor in ITBS. 14,15 Thus, the pathoetiology of ITBS has become a topic of debate with important implications for prevention and management. J Ultrasound Med 2013; 32:

6 By using sonography to evaluate the ITB in an atrisk population of asymptomatic recreational runners, we have clearly documented that the ITB does in fact move anteroposteriorly relative to the LFE within the functional ranges of knee flexion-extension. This study represents the first formal investigation of ITB motion using sonography. Our data show that the anterior ITB-to-LFE distance was reduced as the knee moved from full extension to 30 and 45 of knee flexion. This change was statistically significant in the supine position from 0 to 45 and in the weightbearing position from 0 to 30 and 0 to 45 (Table 1). Although quantitative anteroposterior ITB translation is clearly evident on the basis of our static images, one can perhaps better appreciate the extent of ITB translation during dynamic scanning (Videos 1 and 2). Table 1. Mean Anterior ITB-to-LFE Distances Relative to Knee and Body Position Position Mean, cm a SD P 95% CI Supine extended Supine b , Supine b , Standing extended Standing b , Standing b , N = 20 participants, 40 knees. CI indicates confidence interval. a Positive numbers indicate that the anterior ITB fibers were anterior to the LFE. b Change in the ITB position during that arc of motion. Table 2. Mean Posterior ITB-to-LFE Distances Relative to Knee and Body Position Position Mean, cm SD P 95% CI Supine extended a Supine b , Supine b , Standing extended Standing b , Standing , N = 4 participants, 8 knees. CI indicates confidence interval. a Positive numbers indicate that the posterior ITB fibers were anterior to the LFE. Negative numbers indicate that the posterior ITB fibers were posterior to the LFE. b Change in the ITB position during that arc of motion. Although these data clearly showed that the anterior ITB moved relative to the LFE, we did consider the possibility that this motion may not represent translation. It would be possible for the anterior fibers of the ITB to move closer to the LFE as a function of ITB tightening due to increased tension. This action would manifest as movement of the anterior fibers toward the LFE, while the posterior fibers would remain unchanged (ie, the ITB has a reduction in anteroposterior width) or move anteriorly toward the LFE (ie, the ITB has an even more substantial reduction in anteroposterior width). Consequently, we also obtained sonographic measurements of the relationship between the posterior ITB fibers and the LFE in a subset of 4 of our participants (additional participants were not examined because of the difficulty in identifying the actual posterior margin of the ITB and differentiating it from the fascia with which it blends). The findings in these 4 participants paralleled those for the anterior ITB-to-LFE distances in that the ITB moved posteriorly during the supine 0 to 45, standing 0 to 30, and standing 0 to 45 arcs of motion (Table 2). Given that both the anterior and posterior fibers of the ITB moved posteriorly during knee flexion, it is reasonable to conclude that the ITB does translate to some extent over the LFE during knee flexion. Furthermore, although not formally investigated in this study, as shown in Video 1, the ITB does not appear to become thicker (ie, shorten in the anteroposterior dimension) during flexion but may in fact become thinner, perhaps representing some degree of anterior-posterior stretch. Although we cannot make conclusions based on our small sample size of 4 participants and 8 knees for the posterior ITB-to-LFE measurements, it is of interest to note that the posterior ITB is typically located anterior to the LFE in full extension (Table 2, Figure 4, and Video 2). By 30 of flexion, the posterior ITB moved over the LFE in a posterior direction. Thus, the posterior free edge of the ITB encounters and passes over the LFE during knee flexion. Furthermore, as shown in Video 2, during the early Table 3. Effect of Weight-Bearing Status on ITB Position a Position Δ Supine to Standing, cm b P Full extension c a For anterior ITB to LFE measurements. b Difference in the anterior ITB-to-LFE distance between supine and standing positions. c This positive value indicates that the average ITB position was cm more anterior during standing in full extension versus supine in full extension J Ultrasound Med 2013; 32:

7 phases of knee flexion, we often observed an initial anterior movement of the posterior ITB fibers, followed by a larger posterior translation. As we did not obtain videos on all of our participants, we cannot make conclusions based on these qualitative observations. However, one may reasonably hypothesize that these motions result in concentrated stresses in the posterior ITB. In support of this hypothesis, it is of interest to note that most patients with ITBS have pain along the posterior margin of the ITB rather than the anterior edge. Further investigation may clarify the relationship between posterior ITB motion with respect to the LFE and the development of ITBS. Further discussion of our findings is warranted in the context of recently published research concerning the ITB. First, although our data definitively showed anteroposterior ITB translation during knee flexion, we recognize that some degree of ITB narrowing (ie, reduction in anteroposterior length) may also be occurring, as suggested by Fairclough and colleagues. 14,20,21 Alternatively, there is a possibility that the ITB actually widens during knee flexion, as shown in Video 2. Narrowing or widening of the ITB could be investigated by the methods outlined herein, but based on our experience, this process would be challenging because of the difficulty in reliably identifying the posterior ITB margin. Second, our findings are not necessarily wholly contradictory to those published by Fairclough and colleagues. 14,15 In our opinion, the well-documented fascial attachments of the ITB to the lateral femur may limit anteroposterior ITB motion but do not preclude such motion. Similarly, we believe that anteroposterior and mediolateral ITB motion may occur simultaneously during knee flexion-extension. The major difference between our study and the study by Fairclough and colleagues is the lack of anteroposterior ITB motion in the latter. However, this determination was made simply by external visual inspection, whereas our current investigation used realtime sonography. It is likely that these methodological differences explain the contrasting results. Of note, this investigation supports the previously published magnetic resonance imaging investigation by Muhle and colleagues, 13 which documented posterior translation of the ITB relative to the LFE with knee flexion as measured in a supine position. Our study also suggests that there is a substantial difference in the position of the anterior-most fibers between the non weight-bearing and weight-bearing positions while the knee is in full extension, with the anterior fibers being located more anteriorly in the weight-bearing position when compared to the non weight-bearing position (Table 3). The reason for this observation remains indeterminate because we did not specifically control the degree of knee extension in the supine versus standing position. Whether solely a function of the weight-bearing status (eg, increased knee extension or hyperextension in the weight-bearing position) or a combination of weightbearing and kinetic chain dynamics, the apparent difference in the ITB position between the supine and standing positions suggests the need for future research investigating the role of the weight-bearing status on the ITB position and kinematics. Sonography is optimally suited for such investigation. 24 Several study limitations are worthy of mention. First, we examined a relatively small sample population of 20 participants (40 knees). It is unknown whether a larger study population would substantially alter our results. It is noteworthy that the study was not powered to detect the interactions of the position (supine versus standing) and ITB motion relative to the femur or the effects of the sex and running history on ITB motion. Most of our participants were young women, and it is difficult to know whether our findings would be similar in other populations. Our collection of demographic information is therefore primarily descriptive to support our contention that our study group consisted of an active running group at risk for ITBS. Second, we did not measure the ITB position in a true single-leg standing position, which would simulate the stance phase of running. We simply found this impractical because patient fatigue and leg motion substantially limited the ability of the examiner to identify the ITB fibers and obtain accurate measurements. Future investigations using special positioning devices may be able to examine the ITB in more functional positions. Third, we did not control for hip and ankle positioning, nor did we control for the degree of knee rotation or knee extension during extension in the standing and supine positions, as previously discussed. We simply allowed the participants to assume their most comfortable positions. Although we cannot presume that more specific control of patient positioning would not change some nuances in our results, we do not think that such control would alter the primary finding of this investigation: that the ITB translates relative to the LFE during flexion. Fourth, we did not specifically determine the reliability of our measurements or their accuracy relative to a reference standard. However, our primary goal was to determine changes in the ITB position during knee flexion. Therefore, we were primarily focused on trends in numbers (ie, whether they change progressively during J Ultrasound Med 2013; 32:

8 knee flexion) and not the actual values themselves. Finally, this investigation included only asymptomatic individuals, which was necessary to provide a baseline of normalcy before examining symptomatic populations. In conclusion, the findings of this study suggest that during the initial 45 of knee flexion, the ITB translates posteriorly over the LFE, as revealed by sonography. Thus, ITBS may, at least in part, be related to ITB irritation from a friction-related phenomenon. Further study in a large population, with assessments of reproducibility and correlations with cadaveric dissection, could potentially strengthen these findings. In addition, further investigations should explore whether differences exist in the ITB position or translation when comparing symptomatic and asymptomatic runners. Sonographic evaluation of the ITB may provide further insight into the pathophysiologic mechanisms of ITBS and facilitate the development of more effective treatment strategies. References 1. Ellis R, Hing W, Reid D. Iliotibial band friction syndrome: a systematic review. Man Ther 2007; 12: Fredericson M, Wolf C. Iliotibial band syndrome in runners: innovations in treatment. Sports Med 2005; 35: Noble CA. Iliotibial band friction syndrome in runners. Am J Sports Med 1980; 8: Orchard JW, Fricker PA, Abud AT, Mason BR. Biomechanics of iliotibial band friction syndrome in runners. Am J Sports Med 1996; 24: Richards DP, Barber A, Troop RL. Iliotibial band Z-lengthening. Arthroscopy 2003; 19: Nemeth WC, Sanders BL. The lateral synovial recess of the knee: anatomy and role in chronic iliotibial band friction syndrome. Arthroscopy 1996; 12: Hariri S, Savidge ET, Reinold MM, Zachazewski J, Gill TJ. Treatment of recalcitrant iliotibial band friction syndrome with open iliotibial band bursectomy: indications, technique, and clinical outcomes. Am J Sports Med 2009; 37: Goh LA, Chhem RK, Wang SC, Chee T. Iliotibial band thickness: sonographic measurements in asymptomatic volunteers. J Clin Ultrasound 2003; 31: Bonaldi VM, Chhem RK, Drolet R, Garcia P, Gallix B, Sarazin L. Iliotibial band friction syndrome: sonographic findings. J Ultrasound Med1998; 17: Kaplan EB. The iliotibial tract: clinical and morphological significance. J Bone Joint Surg Am 1958; 40-A: Ekman EF, Pope T, Martin DF, Curl WW. Magnetic resonance imaging of iliotibial band syndrome. Am J Sports Med 1994; 22: Gunter P, Schwellnus MP. Local corticosteroid injection in iliotibial band friction syndrome in runners: a randomised controlled trial. Br J Sports Med 2004; 38: Muhle C, Ahn JM, Yeh L, et al. Iliotibial band friction syndrome: MR imaging findings in 16 patients and MR arthrographic study of six cadaveric knees. Radiology 1999; 212: Fairclough J, Hayashi K, Toumi H, et al. The functional anatomy of the iliotibial band during flexion and extension of the knee: implications for understanding iliotibial band syndrome. J Anat 2006; 208: Fairclough J, Hayashi K, Toumi H, et al. Is iliotibial brand syndrome really a friction syndrome? J Sci Med Sport 2007; 10: Khoury V, Cardinal E, Bureau NJ. Musculoskeletal sonography: a dynamic tool for usual and unusual disorders. AJR Am J Roentgenol 2007; 188:W63 W Nazarian LN, McShane JM, Ciccotti MG, O Kane PL, Harwood MI. Dynamic US of the anterior band of the ulnar collateral ligament of the elbow in asymptomatic major league baseball pitchers. Radiology 2003; 227: Huang L, Stevens KJ, Fredericson M. Dynamic ultrasound to diagnose subluxating biceps femoris tendon over the fibular head: a case report. PM R 2009; 1: Fredericson M, White JJ, MacMahon JM, Andriacchi TP. Quantitative analysis of the relative effectiveness of 3 iliotibial band stretches. Arch Phys Med Rehabil 2002; 83: Wang HK, Ting-Fang Shih T, Lin KH, Wang TG. Real-time morphologic changes of the iliotibial band during therapeutic stretching; an ultrasonographic study. Man Ther 2008; 13: Wang TG, Jan MH, Lin KH, Wang HK. Assessment of stretching of the iliotibial tract with Ober and modified Ober tests: an ultrasonographic study. Arch Phys Med Rehabil 2006; 87: 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: Gyaran IA, Spiezia F, Hudson Z, Maffulli N. Sonographic measurement of iliotibial band thickness: an observational study in healthy adult volunteers. Knee Surg Sports Traumatol Arthrosc 2010; 19: Smith J, Finnoff JT. Diagnostic and interventional musculoskeletal ultrasound, part 2: clinical applications. P MR 2009; 1: J Ultrasound Med 2013; 32: