Quantitative analysis of effectiveness and associated factors of exercise on symptoms in osteoarthritis: a pharmacodynamic model-based meta-analysis.

Objective: This study aims to evaluate the time point and magnitude of peak effectiveness of exercise and the effects of various exercise modalities for osteoarthritis (OA) symptoms and to identify factors that significantly affect the effectiveness of exercise.

Design: Pharmacodynamic model-based meta-analysis (MBMA).

Data sources: Embase, PubMed, Cochrane Library, Web of Science and Scopus were searched for randomised controlled trials (RCTs) examining the effect of exercise for OA from inception to 20 November 2023.

Eligibility criteria: RCTs of exercise interventions in patients with knee, hip or hand OA, using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) subscales or Visual Analogue Scale (VAS) pain scores as outcome measures, were included. The minimum clinically important difference (MCID) for WOMAC total, pain, stiffness, function and VAS pain was 9.0, 1.6, 0.8, 5.4 and 0.9, respectively.

Results: A total of 186 studies comprising 12 735 participants with symptomatic or radiographic knee, hip or hand OA were included. The effectiveness of exercise treatments peaked at 1.6-7.2 weeks after initiation of exercise interventions. Exercise was more effective than the control, but the differences in the effects of exercise compared with control on all outcomes were only marginally different with the MCID (7.5, 1.7, 1.0, 5.4 and 1.2 units for WOMAC total, pain, stiffness, function and VAS pain, respectively). During a 12-month treatment period, local exercise (strengthening muscles and improving mobilisations of certain joints) had the best effectiveness (WOMAC pain decreasing by 42.5% at 12 weeks compared with baseline), followed by whole-body plus local exercise. Adding local water-based exercise (eg, muscle strengthening in warm water) to muscle strengthening exercise and flexibility training resulted in 7.9, 0.5, 0.7 and 8.2 greater improvements in the WOMAC total score, pain, stiffness and function, respectively. The MBMA models revealed that treatment responses were better in participants with more severe baseline symptom scores for all scales, younger participants for the WOMAC total and pain scales, and participants with obesity for the WOMAC function. Subgroup analyses revealed participants with certain characteristics, such as female sex, younger age, knee OA or more severe baseline symptoms on the WOMAC pain scale, benefited more from exercise treatment.

Conclusion: Exercise reaches peak effectiveness within 8 weeks and local exercise has the best effectiveness, especially if local water-based exercise is involved. Patients of female sex, younger age, obesity, knee OA or more severe baseline symptoms appear to benefit more from exercise treatment than their counterparts.