Effects of aquatic exercise on pain and physical function in overweight/obese patients with lower limb osteoarthritis: a systematic review and meta-analysis

BACKGROUND: Previous research has established that aquatic exercise is an effective intervention for alleviating pain and enhancing physical function in patients with lower limb osteoarthritis (OA). However, its specific efficacy for overweight and obese populations, as well as the intervention parameters associated with clinical outcomes in these groups, remain poorly defined. This study aims to assess the effects of aquatic exercise on pain and physical function in this specific demographic and to explore potential intervention-related moderators through subgroup analysis. METHODS: Following the PRISMA guidelines, a systematic search was conducted across the PubMed, Web of Science, Embase, Cochrane Library, and Scopus databases. The search cutoff date was set for February 1, 2026. Emphasis was placed on randomized controlled trials (RCTs) evaluating aquatic interventions for overweight or obese adults with primary knee and/or hip OA. RESULTS: A total of 12 RCTs involving 1,057 participants were included. The random-effects meta-analysis suggested that aquatic exercise was associated with lower pain scores (SMD = -0.36; 95% CI, -0.50 to -0.22; p < 0.001; I² = 18%) and better physical function (SMD = -0.33; 95% CI, -0.46 to -0.20; p < 0.001; I² = 0%). Exploratory subgroup analyses suggested that both overweight and obese patients showed favorable changes in pain and physical function, with numerically larger effects observed in obese patients. Lower volume protocols, including shorter session durations, lower weekly frequency, and shorter intervention periods, tended to show favorable outcomes; however, these subgroup findings should be interpreted as hypothesis-generating rather than confirmatory evidence of an optimal dose-response relationship. CONCLUSION: Aquatic exercise may be associated with modest improvements in pain and physical function among overweight or obese patients with lower limb OA. Exploratory subgroup findings suggested numerically larger effects in obese individuals and favorable outcomes with some lower volume protocols. However, the certainty of evidence was low, and these findings should be interpreted cautiously. Current evidence does not support firm conclusions regarding an optimal aquatic exercise prescription or a definitive dose-response relationship. Aquatic exercise may represent a useful low-impact adjunct to conservative management, but further well-designed trials are needed to confirm clinically meaningful effects and clarify optimal intervention parameters. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420261354574, identifier CRD420261354574.