Impact of Different Exercise Intensities on Progression of Knee Osteoarthritis: A Systematic Review
Abstract
Background: Exercise therapy is a core non-pharmacological treatment for knee osteoarthritis (OA), yet uncertainty remains regarding the comparative long-term effects of moderate-to-vigorous versus low-intensity exercise on pain and functional outcomes. This systematic review examined the existing evidence to determine how exercise intensity influences long-term clinical trajectories among adults with symptomatic knee OA. Methods: A systematic search of randomized controlled trials, longitudinal cohorts, and controlled clinical studies was undertaken. Studies were eligible if they included adults with symptomatic or radiographic knee OA; implemented structured exercise interventions; and reported pain and/or physical function outcomes with follow-up. Databases searched included PubMed, Scopus, CINAHL, Web of Science, and Cochrane CENTRAL from inception to February 2025. Quality assessment was conducted using the Cochrane Risk of Bias tool for RCTs and the Newcastle–Ottawa Scale for observational studies. Results: Eleven eligible studies involving 149–80,893 participants were included. Most trials compared different exercise modalities or delivery approaches rather than explicit intensity levels. Only one pilot RCT prescribed intensity using percentage of one-repetition maximum (1RM) and the Borg Rating of Perceived Exertion (RPE) scale. Across studies, exercise (regardless of intensity description) consistently improved short-term pain and physical function, although benefits diminished after 6–12 months. Long-term effects were more strongly influenced by adherence, self-efficacy, weight change, comorbidities, and supervision frequency. Conclusion: Evidence remains insufficient to determine whether moderate-to-vigorous exercise yields superior long-term outcomes over low-intensity programs in knee OA. Future trials should standardize intensity metrics and incorporate behavioral and multimodal components to enhance the durability of outcomes.