Abstract / Summary
Background/Objectives: Knee osteoarthritis (OA) causes pain, physical function limitations, and reduced quality of life. This updated systematic review compared the effectiveness of aquatic exercise (AE) versus land-based exercise (LBE) on these outcomes in adults with knee OA. Methods: Randomised controlled trials (RCTs) published between September 2018 and July 2025 were included if they compared supervised AE with LBE. PubMed, Web of Science, Scopus, and PEDro were searched. Methodological quality was assessed using the PEDro scale, and the certainty of evidence was evaluated using GRADE. Owing to substantial clinical and methodological heterogeneity in participant characteristics, intervention content and dose, outcome measures, and reporting methods, quantitative pooling was not considered clinically meaningful; therefore, a structured synthesis without meta-analysis was conducted. Results: Nine RCTs enrolling 700 participants were included, of whom 661 contributed directly to the AE versus LBE comparison. Between-group effects varied across outcomes and studies. Differences in pain measured using the VAS generally ranged from −1.80 to −0.32 scale units in favour of AE; however, clinical importance remained uncertain because applicable thresholds were not available for all measures and the confidence interval around the largest estimate included effects below the contextual benchmark. Evidence for physical function and quality of life was inconsistent, and several confidence intervals included no between-group effect or were wide. Although selected outcomes favoured AE, the observed differences were generally small or imprecise, and their clinical importance was frequently uncertain. The certainty of evidence ranged from very low to high and was predominantly low or very low. Conclusions: The evidence included in this update does not establish consistent clinically important superiority of AE over LBE for people with knee OA. Although some between-group estimates favoured AE, most effects were small or imprecise, and confidence in the findings was limited. Exercise modality should therefore be selected according to individual characteristics, preferences, accessibility, and clinical context. Further well-designed multicentre trials with standardised outcome reporting, longer-term follow-up, and comprehensive adherence assessment are needed.