Analysis of Hip Muscle Strength and a Functional Assessment Tool in Subjects with and without Patellofemoral Pain Syndrome

Background and Purpose. Patellofemoral Pain Syndrome (PFPS) is the most prevalent disorder involving theknee. Recently, the lateral hip musculature, specifically weak abductors and external rotators of the hip, has been anecdotally implicated as a potential source of PFPS. At this time there has been little to no research to prove this theory, therefore the purposes of the study were as follows: (1) to determine if individuals with PFPS demonstrated deficits compared to their non-involved limb and/or compared to the control group when performing a functional test (Unilateral Stance Balance with Contralateral Ann Anterior/Lateral Reach designed by Gary Gray); (2) to assess strength with a hand held muscle testing device of the hip external rotators and abductors to determine if deficits exist in the limbs of individuals with PFPS; (3) to determine if there was a correlation between the functional test chosen and the strength measurements of the hip external rotators and abductors. Subjects and Methods. A total of26 subjects (15 asymptomatic and 11 symptomatic) between the ages of 18 and 35 participated in this study. Subjects were chosen based on subjective criteria proposed to be indicative of PFPS. Subjects were first tested performing a functional test, where number of repetitions completed and excursion distance were analyzed. Then the subjects were asked to perform specific strength testing for the gluteus medius and external rotators of the hip. Results. A one-way ANOVA was performed using Limb Symmetry Index (LSI) data to determine whether there was a significant difference between the two groups for any of the dependent variables. Subjects with PFPS had significantly lower LSI values, indicating that the involved legs had a lower level of function, as reflected by the number of repetitions that were performed in 30 seconds during the functional test. From data that was normalized for body weight, it was found that subjects with PFPS affecting their dominant leg performed significantly fewer repetitions (mean 9.0, sd 1.84) on the functional test when compared to the dominant legs of asymptomatic subjects (mean 11.60, sd 3.5). A correlation analysis revealed that there were no significant relationships between performance during any aspect of strength and either component of functional testing. Discussion and Conclusion. The results of this study provide support for part of the hypothesis that individuals with unilateral PFPS would demonstrate decreased performance during functional testing on their involved limb. This data would seem to indicate that decreased endurance of the lateral hip muscles in individuals with PFPS might be one cause of the decreased number of repetitions performed by those individuals with PFPS