Predictors of Hip Internal Rotation During Running An Evaluation of Hip Strength and Femoral Structure in Women With and Without Patellofemoral Pain

Background: Recent studies have suggested that excessive hip internal rotation during dynamic tasks may be associated with patellofemoral pain. Although diminished hip-muscle strength and altered femoral morphologic characteristics have been implicated in abnormal hip rotation in persons with patellofemoral pain, no study has confirmed this hypothesis. Hypothesis: Women with patellofemoral pain would demonstrate increased average hip internal rotation, decreased hip-muscle performance, and abnormal femoral shape compared with controls. Furthermore, measures of hip strength and femoral shape are predictive of average hip internal rotation during running. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Nineteen women with patellofemoral pain and 19 pain-free controls participated. Lower extremity kinematics during running, hip-muscle performance, and femoral morphologic characteristics on magnetic resonance imaging were quantified. Independent t tests were used to assess group differences. Stepwise linear regression was used to determine whether measures of strength and/or structure were predictive of average hip internal rotation during running. Results: Participants with patellofemoral pain demonstrated significantly greater average hip internal rotation (8.2 +/- 6.6 vs 0.3 +/- 3.6; P < .001), reduced hip-muscle strength in 8 of 10 hip strength measurements, and greater femoral inclination (132.8 +/- 5.2 vs 128.4 +/- 5.0; P = .011) compared with controls. Stepwise regression revealed that isotonic hip extension endurance was the only predictor of average hip internal rotation (r = -.451; P = .004). Conclusion: Abnormal hip kinematics in women with patellofemoral pain appears to be the result of diminished hip-muscle performance as opposed to altered femoral structure. The results suggest that assessment of hip-muscle performance should be considered in the evaluation and treatment of patellofemoral joint dysfunction.