The review concluded that outcomes following aquatic exercise for adults with hip or knee arthritis appeared comparable to outcomes following land-based exercise. Aquatic programs provided an alternative for people who found it difficult or were unable to exercise on land. Despite not evaluating pain as an outcome, the authors' conclusions reflect the evidence presented and appear likely to be reliable.

To compare the effects of aquatic exercise with land-based exercise in patients with hip or knee arthritis.

MEDLINE, CINAHL, AMED and the Cochrane Central Register of Controlled Clinical Trials (CENTRAL) were searched from inception up to July 2010 for studies in English; search terms were reported.

Randomised controlled trials (RCTs) of aquatic exercise versus land-based exercise in adults (18 years or older) with rheumatoid arthritis or osteoarthritis were eligible for inclusion. Exercise interventions to improve strength, endurance, resistance or aerobic capacity (whether gym or home-based) were eligible. Trials had to report function, mobility or patient satisfaction outcomes (using any assessment instruments) in a way which allowed significance testing between groups to be performed. Participants who exercised as part of rehabilitation immediately following joint replacement surgery were excluded. Exercise interventions given alongside other interventions were also excluded.

Most trials included patients with osteoarthritis and half the trials included patients with rheumatoid arthritis. Mean participant ages ranged from 55 to 73 years. Interventions were provided one to three times per week, for 30 to 60 minutes, with durations ranging from four to 18 weeks. The components of the interventions also varied, but almost all were supervised. Some interventions also incorporated a home exercise programme. The outcome assessment tools used varied across trials. Trials were published from 1996 to 2009.

Two reviewers independently selected studies for inclusion, with disagreements resolved by discussion, or by a third reviewer.

Trial quality was assessed using the following criteria of the PEDro scale: eligibility criteria specified; random allocation; concealment of allocation; baseline similarity of treatment groups with respect to prognosis; blinding of patients, therapists and assessors; adequacy of follow-up; intention-to-treat analysis; at least one between-group statistical analysis reported; and at least one point estimate and variability for a key outcome reported. Trials were given a score out of 10.

The assessment was performed by one reviewer with the results compared with published PEDro scores conducted by other reviewers when available (when published scores were not available a second reviewer performed an assessment). If there were disagreements another reviewer performed an assessment.

Baseline and end of treatment data were extracted to calculate standardised mean differences with 95% confidence intervals (CI). Medians were used as best estimates of means. Long-term data were not extracted. Intention-to-treat data were prioritised over per-protocol data when possible. Although around half the trials had a (third) control arm, comparisons with control groups were beyond the scope of this publication.

Two reviewers independently extracted the data, with disagreements resolved by discussion.

Meta-analyses were performed to calculate pooled standardised mean differences, with 95% confidence intervals. A random-effects model was used when the heterogeneity Ι² value was more than 50%, otherwise a fixed-effect model was used. A standardised mean difference of less than 0.2 was considered a small effect, 0.5 (less than 0.2 and up to 0.8) was considered a moderate effect, and larger than 0.8 a large effect.

Ten RCTs were eligible for inclusion (659 participants, range 22 to 115). PEDro quality assessment scores ranged from 5 to 8 out of 10.

There was no statistically significant difference in functional outcomes between water based compared to land-based exercise groups. Following removal of one trial with a significant baseline imbalance, the standardised mean difference was 0.07 (95% CI -0.26 to 0.12, 7 trials) and there was no heterogeneity. There was also no statistically significant difference between groups for mobility (seven trials, Ι² not reported), dynamic balance (three trials, Ι²=52%), indices evaluating multiple health domains (five trials, Ι²=58%), and for the analysis pooling function plus multiple health domain indices (nine trials, Ι²=33%).

One trial reported measures of patient perception of the interventions, finding no difference between exercise groups for enjoyment.

Outcomes following aquatic exercise for adults with arthritis appeared to be comparable to land-based exercise. When people were unable to exercise on land, or found land-based exercise difficult, aquatic programs provided an enabling alternative strategy.

The review addressed a clear question and was supported by reproducible eligibility criteria. Several relevant electronic databases were searched, but the restriction to searching only for studies in English meant that some relevant trials may have been missed. It was unclear whether unpublished trials were sought. Therefore, the possibility of language or publication biases affecting the review results could not be ruled out. Suitable methods (such as independent duplicate processes) were used to reduce the risk of reviewer error and bias throughout the review.

Trial quality was assessed and the results were used to guide sensitivity analyses. Comprehensive trial details were provided. Appropriate methods were used to pool data and to assess and investigate heterogeneity. However, sensitivity analyses by type of arthritis were not reported, so the review results related only to a mixed population.

The review did not specifically examine the effect of the interventions on pain, an important outcome in this patient population; although most studies reported pain levels at baseline, it was unclear how many reported pain results at the end of treatment. The results also related to short-term comparisons. Nevertheless, the authors' conclusions are a fair reflection of the evidence presented, and appear likely to be reliable.

Practice: The authors stated that, for people who have significant mobility or function limitations and are unable to exercise on land, aquatic exercise appeared to be a legitimate alternative that may enable people to successfully participate in exercise. Clinical decision making on exercise choice should consider patients’ specific requirements and disabilities, patients’ preferences, therapist expertise, and best available evidence along with practical considerations such as availability and cost.

Research: The authors stated that high quality trial design, with intention-to-analysis, adequate follow-up and baseline similarity, would advance the quality of work in this field. The authors also noted a lack of information on patient satisfaction or adherence to exercise interventions, despite the importance of patient engagement in exercise programmes.

No external funding.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.