Understanding how changes in physical and psychological factors following therapeutic exercise are associated with treatment outcome could have important implications for refining rehabilitation programs for knee osteoarthritis (OA). The objective of this study was to examine the association of changes in these factors with changes in pain and function after an exercise program for people with knee OA.


In total, 152 people with knee OA completed an exercise program consisting of lower extremity strengthening, stretching, range of motion, balance and agility, and aerobic exercises. The change from baseline to the 2-month followup was calculated for physical and psychological factors, including self-reported knee instability, quadriceps strength, knee and ankle range of motion, lower extremity muscle flexibility, fear of physical activity, anxiety, and depressive symptoms. Treatment response was defined as a minimum of a 20% improvement from baseline in both a numerical knee pain rating scale and the Western Ontario and McMaster Universities Osteoarthritis Index physical function scale. The association of each factor with treatment response was examined with logistic regression mutually adjusted for age, sex, body mass index, radiographic severity, and exercise group.


Change in self-reported knee instability (odds ratio [OR] 1.67 [95% confidence interval (95% CI) 1.13–2.47]) and fear of physical activity (OR 0.93 [95% CI 0.88–1.00]) were the only 2 factors that were significantly associated with treatment response after adjustment for covariates.


Improvement in knee instability and fear of physical activity were associated with increased odds of a positive treatment response following therapeutic exercise in subjects with knee OA.