Abstract
OBJECTIVE: To investigate the movement and muscle activation strategies during walking of individuals with medial knee osteoarthritis (OA) to determine the influence of quadriceps strength, medial knee laxity, limb alignment, and self-reported knee instability on knee motion. METHODS: Twenty-eight persons with medial knee OA and 26 control subjects participated. Quadriceps strength, medial knee laxity, and limb alignment were measured. Knee instability (I(KOS) score) was assessed with the Activities of Daily Living Scale of the Knee Outcome Survey. Knee motion and muscle activation patterns were measured with motion analysis. Group differences were detected with independent samples t-tests and predictive relationships were determined with linear and hierarchical regression analyses. RESULTS: Individuals with OA were weaker, had greater medial knee laxity, and had more varus alignment. The OA group used less knee motion and higher muscle co-contraction during weight acceptance and single-limb support. Quadriceps strength and I(KOS) score significantly strengthened the prediction of knee motion during weight acceptance and single-limb support, whereas limb alignment and medial laxity did not. CONCLUSION: The knee stiffening and higher muscle co-contraction used by the OA group may be detrimental to joint integrity. I(KOS) scores predicted knee motion after accounting for quadriceps strength, underscoring the importance of addressing knee instability with appropriate rehabilitation strategies in persons with medial knee OA in order to promote long-term joint integrity.