Efficacy and potential determinants of exercise therapy in knee and hip osteoarthritis: A systematic review and meta-analysis

BACKGROUND: Exercise is an effective treatment for osteoarthritis. However, the effect may vary from one patient (or study) to another. OBJECTIVE: To evaluate the efficacy of exercise and its potential determinants for pain, function, performance, and quality of life (QoL) in knee and hip osteoarthritis (OA). METHODS: We searched 9 electronic databases (AMED, CENTRAL, CINAHL, EMBASE, MEDLINE Ovid, PEDro, PubMed, SPORTDiscus and Google Scholar) for reports of randomised controlled trials (RCTs) comparing exercise-only interventions with usual care. The search was performed from inception up to December 2017 with no language restriction. The effect size (ES), with its 95% confidence interval (CI), was calculated on the basis of between-group standardised mean differences. The primary endpoint was at or nearest to 8 weeks. Other outcome time points were grouped into intervals, from < 1 month to ≥ 18 months, for time-dependent effects analysis. Potential determinants were explored by subgroup analyses. Level of significance was set at P ≤ 0.10. RESULTS: Data from 77 RCTs (6472 participants) confirmed statistically significant exercise benefits for pain (ES 0.56, 95% CI 0.44–0.68), function (0.50, 0.38–0.63), performance (0.46, 0.35–0.57), and QoL (0.21, 0.11–0.31) at or nearest to 8 weeks. Across all outcomes, the effects appeared to peak around 2 months and then gradually decreased and became no better than usual care after 9 months. Better pain relief was reported by trials investigating participants who were younger (mean age < 60 years), had knee OA, and were not awaiting joint replacement surgery. CONCLUSIONS: Exercise significantly reduces pain and improves function, performance and QoL in people with knee and hip OA as compared with usual care at 8 weeks. The effects are maximal around 2 months and thereafter slowly diminish, being no better than usual care at 9 to 18 months. Participants with younger age, knee OA and not awaiting joint replacement may benefit more from exercise therapy. These potential determinants, identified by study-level analyses, may have implied ecological bias and need to be confirmed with individual patient data.