Effect of a home program of hip abductor exercises on knee joint loading, strength, function, and pain in people with knee osteoarthritis: a clinical trial.

BACKGROUND Hip abductor muscle weakness may result in impaired frontal-plane pelvic control during gait, leading to greater medial compartment loading in people with knee osteoarthritis (OA). OBJECTIVE This study investigated the effect of an 8-week home strengthening program for the hip abductor muscles on knee joint loading (measured by the external knee adduction moment during gait), strength (force-generating capacity), and function and pain in individuals with medial knee OA. DESIGN The study design was a nonequivalent, pretest-posttest, control group design. SETTING Testing was conducted in a motor performance laboratory. PATIENTS An a priori sample size calculation was performed. Forty participants with knee OA were matched for age and sex with a control group of participants without knee OA. INTERVENTION Participants with knee OA completed a home hip abductor strengthening program. MEASUREMENTS Three-dimensional gait analysis was performed to obtain peak knee adduction moments in the first 50% of the stance phase. Isokinetic concentric strength of the hip abductor muscles was measured using an isokinetic dynamometer. The Five-Times-Sit-to-Stand Test was used to evaluate functional performance. Knee pain was assessed with the Western Ontario and McMaster Universities Osteoarthritis Index questionnaire. RESULTS Following the intervention, the OA group demonstrated significant improvement in hip abductor strength, but not in the knee adduction moment. Functional performance on the sit-to-stand test improved in the OA group compared with the control group. The OA group reported decreased knee pain after the intervention. LIMITATIONS Gait strategies that may have affected the knee adduction moment, including lateral trunk lean, were not evaluated in this study. CONCLUSIONS Hip abductor strengthening did not reduce knee joint loading but did improve function and reduce pain in a group with medial knee OA.