Association of Dynamic Joint Power With Functional Limitations in Older Adults With Symptomatic Knee Osteoarthritis

Objectives: To determine which lower-limb joint moments and powers characterize the level of gait performance of older adults with symptomatic knee osteoarthritis (OA). Design: Cross-sectional observational study. Setting: University motion analysis laboratory. Participants: Community-dwelling adults (N=60; 27 men, 33 women; age 50-79y) with symptomatic knee OA. Interventions: Not applicable. Main Outcome Measures: Physical function was measured using the long-distance corridor walk, the Short Physical Performance Battery, and the Late Life Function and Disability Instrument (LLFDI Function). Joint moments and power were estimated using an inverse dynamics solution after 3-dimensional computerized motion analysis. Results: Subjects aged 64.2 +/- 7.4 years were recruited. Ranges (mean +/- SD) for the 400-m walk time and the LLFDI Advanced Lower-Limb Function score were 215.3 to 536.8 (304.1 +/- 62.3) seconds and 31.5 to 100 (57.0 +/- 14.9) points, respectively. In women, hip abductor moment (loading response), hip abductor power (midstance), eccentric hamstring moment (terminal stance), and power (terminal swing) accounted for 41%, 31%, 14%, and 48% of the variance in the 400-m walk time, respectively (model R(2)=.61, P<.003). In men, plantar flexor and hip flexor power (preswing) accounted for 19% and 24% of the variance in the 400-m walk time, respectively (model R(2)=.32, P=.025). Conclusions: There is evidence that men and women with higher mobility function tend to rely more on an ankle strategy rather than a hip strategy for gait. In higher functioning men, higher knee extensor and flexor strength may contribute to an ankle strategy, whereas hip abductor weakness may bias women with lower mobility function to minimize loading across the knee via use of a hip strategy. These parameters may serve as foci for rehabilitation interventions aimed at reducing mobility limitations.