Relationship Between Lower-Extremity Strength and Subjective Function in Individuals With Patellofemoral Pain

Objective: Evaluate the relationship between subjective knee function and lower-extremity strength in individuals with patellofemoral pain (PFP). Design: Cohort. Setting: Laboratory. Participants: Participants were 30 individuals with PFP (20 females and 10 males; 76.02 [17.88] kg, 173.04 [7.58] cm, and 24.9 [7] y). Main Outcome Measures: Subjects completed the Activities of Daily Living Scale (ADLS) and had lower-extremity hip and knee isometric strength assessed. Strength was compared between low and high subjective functioning ADLS groups. Correlations for strength and subjective function were assessed, with a linear regression utilized to determine if strength predicted subjective function. Results: Quadriceps strength was significantly greater in the high subjective function group (38.5 [13.9] percent body mass) than in the low subjective function group (27.88 [8.96] percent body mass, P = .02). Significant correlations were seen between the ADLS and all 5 lower-extremity strength measures (r = .376-.535). Quadriceps strength was a strong predictor of subjective function in those with PFP, explaining 28.6% of the total variance in the ADLS. Conclusions: Quadriceps strength was a strong predictor of subjective function when assessed by the ADLS in patients with PFP and significantly greater in those with higher subjective function. A strong relationship exists between self-reported function and lower-extremity strength, suggesting the need to evaluate and treat lower-extremity weakness.