How does exercise, with and without diet, improve pain and function in knee osteoarthritis? A secondary analysis of a randomised controlled trial exploring potential mediators of effects.

OBJECTIVE: Explore mediators of effects of two 6-month telehealth-delivered exercise programs, with and without weight loss diet, on pain and function improvements in knee osteoarthritis.

METHODS: Secondary analysis of 345 participants from a three-arm randomised controlled trial of exercise (Exercise) and exercise plus diet (Diet+Exercise) versus information (Control). Outcomes were changes in pain (11-point Numeric Rating Scale) and function (WOMAC, 0-68) at 12-months. Potential mediators were change at 6 months in i) attitudes towards self-management, ii) fear of movement, iii) arthritis self-efficacy, iv) weight, v) physical activity, and vi) willingness for knee surgery. For Diet+Exercise vs Exercise, only change in weight was evaluated.

RESULTS: Possible mediators of Exercise vs Control included reduced fear of movement (accounting for -1.11 [95% confidence interval: -2.15, -0.07] units improvement in function) and increased arthritis self-efficacy (-0.40 [-0.75, -0.06] reduction in pain, -1.66 [-3.04, -0.28] improvement in function). Diet+Exercise vs Control mediators included reduced fear of movement (-1.13 [-2.17, -0.08] improvement in function), increased arthritis self-efficacy (-0.77 [-1.26, -0.28] reduction in pain, -5.15 [-7.34, -2.96] improvement in function), and weight loss (-1.20 [-1.73, -0.68] reduction in pain, -5.79 [-7.96, -3.63] improvement in function). Weight loss mediated Diet+Exercise vs Exercise (-0.89 [-1.31, -0.47] reduction in pain, -4.02 [-5.77, -2.26] improvement in function).

CONCLUSION: Increased arthritis self-efficacy, reduced fear of movement, and weight loss may partially mediate telehealth-delivered exercise program effects, with and without diet, on pain and/or function in knee osteoarthritis. Weight loss may partially mediate the effect of diet plus exercise, compared to exercise alone. This article is protected by copyright. All rights reserved.