The authors assessed the efficacy of aerobic walking and home-based quadriceps strengthening exercises in reducing pain and disability in patients with knee osteoarthritis. Both interventions were found to be more effective than no exercise. However, the findings were based on poor-quality trials which may compromise the validity of the conclusions. Direct comparisons between the two interventions are warranted.

To assess the efficacy of aerobic walking and home-based quadriceps strengthening exercises in reducing pain and disability in knee osteoarthritis.

MEDLINE, EMBASE, CINAHL, PEDro and the Cochrane Controlled Trials Register were searched from 1966 to 2003 for studies published in English; the search terms were reported. The reference lists from retrieved studies and reviews were screened for further eligible studies. Abstracts alone were excluded.

Randomised controlled trials (RCTs) were eligible for inclusion.

Studies of aerobic walking or home-based quadriceps strengthening exercises compared with a non-exercise control group were eligible for inclusion. Exercise was deemed to be home-based if it was undertaken exclusively in the participant's home setting, or if partly supervised the exercise was expected to be continued at home unsupervised. Peri-operative exercise regimens were excluded.

Studies of participants with knee osteoarthritis were eligible for inclusion. Studies recruiting patients with osteoarthritis of other joints were included if the results for the knee were available separately. The participants in the aerobic exercise trials had a mean age between 69 and 70.1 years, whereas those in the strengthening exercise trials had a mean age between 61.9 and 73.7 years.

Studies that measured pain and/or self-reported disability were eligible for inclusion. Pain was the primary outcome measure. The measures used to assess pain in the included trials were not reported.

The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.

The Jadad scale was used to assess the validity of the studies. This scale measures randomisation, double-blinding, and withdrawals and drop-outs, and gives a score between 0 and 5. Two reviewers independently assessed the validity of the studies.

Two reviewers independently extracted the data from the studies. Such data included the mean pain scores and reported disability, with standard deviations, at baseline and final follow-up to enable the calculation of the mean change for each trial arm. This was then used to calculate the mean difference and 95% confidence interval (CI) for each trial.

The pooled weighted mean difference (WMD) and 95% CI were calculated in separate meta-analyses according to whether the exercise regimen involved aerobic or strengthening exercises. A prior publication was cited for the methodology used (see Other Publications of Related Interest).

Heterogeneity was assessed using the Q statistic. When RCTs were heterogeneous a random-effects model was used. The results from both the fixed-effect and random-effects meta-analyses were reported when statistically significant heterogeneity was not observed.

Thirteen RCTs were included. Three studies assessed aerobic walking (n=156), nine assessed home-based quadriceps strengthening exercises (n=1,709) and one assessed both aerobic walking and home-based strengthening exercises (n=439).

The Jadad scores ranged from 1 to 3 (out of 5), with none of the trials reporting to be double-blinded.

Pain was reduced significantly more with aerobic exercise than with no exercise (WMD 0.52, 95% CI: 0.34, 0.70; 4 RCTs, n=449). Participants in the aerobic exercise group reported less disability than those in the no exercise group (WMD 0.46, 95% CI: 0.25, 0.67; 2 RCTs, n=385). No statistically significant heterogeneity was detected for either analysis.

Pain was reduced significantly more with home-based quadriceps strengthening exercises than with no exercise (WMD 0.32, 95% CI: 0.23, 0.42; 11 RCTs, n=2,004). One study, with a large effect size, was excluded from this meta-analysis due to concomitant medication and a sham exercise programme delivered in the control group. Participants in the quadriceps strengthening exercise group reported less disability than those in the no exercise group (WMD 0.32, 95% CI: 0.23, 0.41; 11 RCTs, n=2,004). No statistically significant heterogeneity was detected for either analysis.

Both aerobic walking and home-based quadriceps strengthening exercise are effective in reducing pain and disability in people with knee osteoarthritis, and appear equally effective when an indirect comparison is made.

The research question and inclusion criteria were clearly stated. The search for studies was comprehensive, although there was no attempt to search for non-English language studies, which may introduce language bias. The data extraction and quality assessment were carried out in duplicate, thus reducing the potential for error and bias. However, it was unclear whether the same methods were employed at the study selection stage. Validity was assessed using appropriate criteria, and the results of the assessment were discussed. The decision to combine the studies in meta-analyses, grouped according to outcome and intervention, seemed appropriate, although there was no information on the outcome measures used in the different studies. The conclusions follow from the data presented, however, the poor-quality trials may compromise the reliability of the findings.

Practice: Offering patients the choice between two effective interventions has the potential to improve adherence and hence outcome.

Research: Direct comparisons between aerobic walking and home-based quadriceps strengthening exercises are required to identify the relative efficacies.

Arthritis Research Campaign, ICAC grant number D0593.

Zhang WY, Li Wan Po A. Analgesic efficacy of paracetamol and its combination with codeine and caffeine in surgical pain: a meta-analysis. J Clin Pharmacol Ther 1996;21:261-82.

This additional published commentary may also be of interest. Schattner A. Review: both aerobic and home-based quadriceps strengthening exercises reduce pain and disability in knee osteoarthritis. ACP J Club 2005;143:71.

This record is a structured abstract written by CRD reviewers. The original has met a set of quality criteria. Since September 1996 abstracts have been sent to authors for comment. Additional factual information is incorporated into the record. Noted as [A:....].