This study aimed to identify the optimal exercise program characterized by type and intensity of exercise, length of exercise program, duration of individual supervised sessions, and number of sessions per week for reducing pain and patient-reported disability in knee osteoarthritis. A systematic review and meta-analysis of randomized controlled trials were performed. Standardized mean differences (SMD) were combined using a random effects model. Study-level covariates were applied in meta-regression analyses in order to reduce the between study heterogeneity. Forty-eight trials were included. Similar effects in reducing pain were found for aerobic, resistance and performance exercise (SMD: 0.67, 0.62 and 0.48; P=0.733). These single type exercise programs were more effective than mixing different exercise types (SMD: 0.61 vs. 0.16; P<0.001). The effect of aerobic exercise on pain relief increased with a larger number of supervised sessions (slope: 0.022 [95%CI: 0.002; 0.043]. Greater pain reduction occurred with quadriceps-specific exercise compared with lower-limb exercise (SMD: 0.85 vs. 0.39; P=0.005); and when supervised exercise was performed at least three times a week (SMD: 0.68 vs. 0.41; P=0.017). No impact of intensity, duration of individual sessions or patient characteristics was found. Similar results were found analyzing the effect on patient-reported disability.
This study concluded that optimal exercise programs for knee OA should have one aim and focus on improving aerobic capacity, quadriceps muscle strength or lower extremity performance. For best effect, the program ought to be supervised and carried out three times a week. Programs like this have similar effect regardless of patient characteristics, including radiographic severity and baseline pain.