Effect of the Frequency and Duration of Land-based Therapeutic Exercise on Pain Relief for People with Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

[Purpose] This study aimed to investigate the influence of land-based exercise frequency and duration on pain relief for people with knee osteoarthritis (OA). [Subjects and Methods] The systematic review included randomized controlled trials that investigated this influence, which were identified by searches of PubMed, the Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature. The exercise groups in the identified trials were categorized according to their type, frequency, and duration of exercise, and subgroup analyses were performed. [Results] Data integration of 17 studies (23 exercise groups) revealed a significant effect and a medium effect size. In subgroups involving strengthening exercise programs of ≥9 weeks duration, heterogeneity was found between subjects who performed up to 3 sessions/week and those who performed ≥4 sessions/week. In subgroups involving strengthening exercise programs of up to 3 sessions/week, there was heterogeneity between subjects who exercised for up to 8 weeks and those who exercised for ≥9 weeks. Heterogeneity was not confirmed in aerobic exercise subgroups. [Conclusion] Differences in exercise frequency and duration influence pain relief in effects of strengthening exercises but do not influence the effect size of aerobic exercise for people with knee OA.