Moving to Maintain Function in Knee Osteoarthritis: Evidence From the Osteoarthritis Initiative

Objectives: To investigate the association between baseline physical activity and I-year functional performance in adults with knee osteoarthritis (OA). Design: Prospective cohort study of knee OA development and progression with 1-year follow-up. Setting: Community. Participants: Osteoarthritis Initiative public data on adults with knee OA (n=2274; age, 45-79y) who participated in functional performance assessments (timed 20-m walk and chair stand test) at baseline and 1-year follow-up. Interventions: Not applicable. Main Outcome Measure: A good 1-year performance Outcome (separately defined for walk time and chair stand measures) was improvement from baseline quintile or maintenance in the best quintile. Results: Almost 2 in 5 persons with radiographic knee OA improved or maintained high performance at 1 year. Physical activity measured by the Physical Activity Scale for the Elderly (PASE) was significantly associated with good walk rate and chair stand outcomes (odds ratio per 40 units PASE [95% confidence interval]=1.13 [1.13, 1.17] and 1.10 [1.05, 1.15], respectively), as were participation in sports/recreational activities (1.45 [1.23, 1.71] and 1.29 [1.09, 1.51], respectively) and lifestyle activities (1.11 [1.06, 1.16] and 1.09 [1.04, 1.14], respectively). An independent protective relationship for these physical activity measures approached significance after adjusting for sociodemographic and health factors. Older adults reported the least baseline physical activity and least frequent good 1-year outcomes. Conclusions: These findings support public health recommendations to be physically active in order to preserve function for persons with knee OA. Physical activity messages should specifically target older adults whose low activity levels may jeopardize their ability to maintain functional performance.