DISCUSSION
Both aerobic walking and home based quadriceps strengthening
exercises are effective at reducing pain and disability in
subjects with knee osteoarthritis. No advantage of one form
of exercise over the other was found on indirect comparison
of pooled data. That both interventions are effective has
implications for clinical practice. Adherence is a major
predictor of response to exercise, and offering patients the
choice between two effective interventions has the potential
to improve adherence and hence outcome. To make a full
comparison of the relative efficacy of aerobic walking and
quadriceps strengthening exercise requires an adequately
powered RCT, and a factorial design would allow the
interaction between both forms of exercise to be investigated.
The RCTs of strengthening exercise produced similar effect
sizes for pain, apart from one study which had a much larger
effect size of 1.36 (95% CI, 1.03 to 1.69).40 This study differed
in its methodology by prescribing the NSAID, oxaprozin, to
all participants and also by exposing the control group to a
‘‘sham’’ exercise programme in an attempt to achieve double
blinding. This study was not pooled, with the effect that the
pooled effect size was reduced slightly from 0.40 to 0.32. The
pooled data also became homogeneous on exclusion of this
study, allowing the use of a fixed effects model. The study
was excluded on similar grounds by the recent Cochrane