Analysis of hip strength in females seeking physical therapy treatment for unilateral patellofemoral pain syndrome.

STUDY DESIGN Cross-sectional. OBJECTIVES To investigate whether females seeking physical therapy treatment for unilateral patellofemoral pain syndrome (PFPS) exhibit deficiencies in hip strength compared to a control group. BACKGROUND Decreased hip strength may be associated with poor control of lower extremity motion during weight-bearing activities, leading to abnormal patellofemoral motions and pain. Previous studies exploring the presence of hip strength impairments in subjects with PFPS have reported conflicting results. METHODS AND MEASURES Twenty females, aged 12 to 35 years, participated in the study. Ten subjects with unilateral PFPS were compared to 10 control subjects with no known knee pathologies. Hip abduction, extension, and external rotation strength were tested using a handheld dynamometer. A limb symmetry index (LSI) was used to quantify physical performance for all tests. RESULTS The symptomatic limbs of subjects with PFPS exhibited impairments in hip strength for all variables tested. LSI values in subjects with PFPS (range, 71%-79%) were significantly lower than those in control subjects (range, 93%-101%) (P< or =.007). A secondary analysis of data normalized to body mass demonstrated that the symptomatic limbs of subjects with PFPS had 52% less hip extension strength (P<.001), 27% less hip abduction strength (P = .007), and 30% less hip external rotation strength (P= .004) when compared to the weaker limbs of control subjects. CONCLUSION Females aged 12 to 35 presenting with unilateral PFPS demonstrate significant impairments in hip strength compared to control subjects when LSI values or body mass normalized values are used to quantify physical performance of the symptomatic limb.