An Anatomic Investigation of the Ober Test.

BACKGROUND: Recent studies have questioned the importance of the iliotibial band (ITB) in lateral knee pain. The Ober test or modified Ober test is the most commonly recommended physical examination tool for assessment of ITB tightness. No studies support the validity of either Ober test for measuring ITB tightness.

PURPOSE/HYPOTHESIS: The purpose of this study was to assess the effects of progressive transection of the ITB, gluteus medius and minimus (med/min) muscles, and hip joint capsule of lightly embalmed cadavers on Ober test results and to compare them with assessment of all structures intact. In addition, thigh position change between gluteus med/min transection and hip capsule transection was also assessed for both versions of the Ober test. It was hypothesized that transection of the ITB would significantly increase thigh adduction range of motion as measured by an inclinometer when performing either Ober test and that subsequent structure transections (gluteus med/min muscles followed by the hip joint capsule) would cause additional increases in thigh adduction.

STUDY DESIGN: Controlled laboratory study.

METHODS: The lower limbs of lightly embalmed cadavers were assessed for midthigh ITB transection versus intact by use of the Ober (n = 28) and modified Ober (n = 34) tests; 18 lower limbs were assessed for all conditions (intact band, followed by sequential transections of the ITB midthigh, gluteus med/min muscles, hip joint capsule) by use of both Ober tests. Paired t tests were used to compare changes in Ober test results between conditions.

RESULTS: No significant changes in thigh position (adduction) occurred in either version of the Ober test after ITB transection. Significant differences were noted for intact band versus gluteus med/min transection and intact band versus hip joint capsule transection (P < .0001) for all findings for both tests. Mean inclinometer measurements for the modified Ober were 4.28° (n = 34 for intact vs ITB transection comparisons), 3.33° (n = 18 for subsequent intact vs gluteus muscle and hip capsule transection comparisons), 5.00° (n = 34 for midthigh ITB transection), 11.20° (gluteus med/min transection), and 13.20° (hip capsule transection). For the Ober test, measures were -2.90° (n = 28 for intact vs ITB transection comparisons), -2.20° (n = 18 for subsequent intact vs gluteus muscle and hip capsule transection comparisons), -2.20° (n = 34 for midthigh ITB transection), 6.50° (gluteus med/min transection), and 9.53° (hip capsule transection). Statistically significant differences were also noted between test findings comparing gluteus med/min transection to hip capsule transection (Ober, P < .0001; modified Ober, P = .0036).

CONCLUSION: The study findings refute the hypothesis that the ITB plays a role in limiting hip adduction during either version of the Ober test and question the validity of these tests for determining ITB tightness. The findings underscore the influence of the gluteus medius and minimus muscles as well as the hip joint capsule on Ober test findings.

CLINICAL RELEVANCE: The results of this study suggest that the Ober test assesses tightness of structures proximal to the hip joint, such as the gluteus medius and minimus muscles and the hip joint capsule, rather than the ITB.