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.