Pain and Hip Lateral Rotator Muscle Strength Contribute to Functional Status in Females with Patellofemoral Pain

Background and Purpose. Patellofemoral pain (PFP) is a common musculoskeletal pain condition, especially in females. Decreased hip muscle strength has been implicated as a contributing factor, yet the relationships between pain, hip muscle strength and function are not known. The purpose of this study was to test the hypothesis that pain and hip muscle strength explain unique portions of variance in the functional status of females with PFP. Methods. An observational, cohort study was conducted. The subjects for this study were twenty-one females with PFP (age: 26 +/- 7 years; height: 163 +/- 4 cm; and body mass: 62 +/- 10 kg). Subjects had a minimum pain duration of two months (mean pain duration: 4.9 +/- 3.6 years). The main measures were pain during a unilateral squat, measured with a visual analogue scale; isometric muscle force of gluteus medius, gluteus maximus and hip lateral rotators; and Kujala score (self-report measure of function). Hierarchical multiple regression analysis was performed with Kujala score as the dependent variable. Pain and hip lateral rotator muscle strength were independent variables, entered in that order. Other strength measures were not correlated with the Kujala score, and as such, were not used in the analysis. Results. Pain explained 22% of the variance in the Kujala score (p = 0.03). Hip lateral rotator strength explained an additional 14% of the variance, after accounting for pain level (p = 0.06). Conclusions. Pain and hip lateral rotator strength contributed to the functional status of females with PFP. Improving pain and hip lateral rotator muscle strength may improve function in females with this common pain condition. Copyright (C) 2009 John Wiley & Sons, Ltd.