Currently, there is a lack of information to support the benefit of performing exercise for relieving hip OA pain. So far, only 1 RCT has assessed the hip as the index joint with OA (28
) with a positive result. The overall results of our meta-analysis showed a significant treatment effect in favor of exercise, but moderate to high heterogeneity among trials was present. Furthermore, we found a stronger favorable effect of exercise when we excluded the trial that was the source of heterogeneity. This latter study used a different prescribed exercise strategy (no therapeutic exercise) and poor exercise adherence, which may have accounted for its unique results.
Exercise trials in lower extremity OA have reported small (0.2) to moderate (0.7) ES for pain (37
). These effects could be compared with pharmacologic treatment such as acetaminophen (ES = 0.2) and NSAIDs (ES = 0.69 only for hip joint) (8
). Here, we found a small benefit of exercise in patients with coexistent hip and knee OA (ES = −0.38), as in a subset of patients with hip as the index joint with OA (ES = −0.43).
First, we decided to include the study by Ravaud et al because it was by far the largest trial addressing exercise in patients with lower extremity OA and because it met our inclusion criteria. Nevertheless, we considered this study to be different from the rest of the trials in the meta-analysis because it was the only one that used an unsupervised exercise program where exercise was not taught personally by a health professional at least once. Moreover, as the authors have previously commented (13
), it is possible that the participants did not carry out exercises properly. There was also a poor compliance (2 of 3 subjects did not attain the specified adherence standard); however, the impact of this factor is still controversial (38
). Therefore, in the remainder of the trials in our meta-analysis, exercise regimens were taught personally to subjects by a physiotherapist (therapeutic exercise) at least once.
Currently, the most effective therapeutic exercise for lower extremity OA involves regular aerobic activity and/or a strengthening program (4
). For knee OA, 2 meta-analyses have not shown any association between pain relief and exercise intensity (24
) or duration of the program or frequency of sessions (39
Among the trials included in our meta-analysis, one common element was the performance of strengthening exercise and repeated in-person attempts to refine and individualize the program, suggesting that this type of exercise might be effective. Although not necessarily a comprehensive assessment of adverse events, the data from these trials suggest that exercise may be safe in these patients.
The current meta-analysis has limitations. First, because most of the data (with the exception of 2 trials) were obtained from trials where hip and knee OA were originally combined but not stratified, it is possible that when we selected only those subjects with hip OA, the initial randomization of the treatment and control groups was lost. Second, post hoc removal of trial data from a meta-analysis may lead to misleading conclusions (40
). However, this strategy has been used when individual study results are in conflict or for the generation of new hypotheses (41
). In our sensitivity analysis, we removed a trial in which the administration of exercise was remote and not provided by a health professional, a qualitatively different strategy than the other trials. Ultimately, combining data from multiple small trials on patients with hip OA may not be equivalent to carrying out a trial in which direct teaching of exercise is used and a large number of patients is enrolled.
Even so, our meta-analysis provides insight into the effectiveness of exercise therapy for pain relief in patients with hip OA. Overall, we found a small favorable effect for therapeutic exercise; moreover, when we focused on trials of subjects with hip as the index joint with OA, this effect was moderate. This leads us to suggest that therapeutic exercise constitutes efficacious treatment for pain in patients with hip OA.