RESUMO
OBJECTIVE: Conduct a systematic review and use meta-analytic techniques to estimate the proportion of total treatment effect that can be attributable to contextual effects (PCE) in adults receiving nonpharmacological, nonsurgical (NPNS) treatments for knee osteoarthritis (OA). DESIGN: We reviewed the published literature to identify five frequently studied NPNS treatments for knee OA: exercise, acupuncture, ultrasound, laser, and transcutaneous electrical nerve stimulation (TENS). We searched for randomized controlled trials (RCTs) of these treatments and abstracted pre- and post-intervention pain scores for groups receiving placebo and active treatments. For each study we calculated the PCE by dividing the change in pain in the placebo group by the change in pain in the active treatment group. We log transformed the PCE measure and pooled across studies using a random effects model. RESULTS: We identified 25 studies for analysis and clustered the RCTs into two groups: acupuncture and topical energy modalities (TEM). 13 acupuncture studies included 1,653 subjects and 12 TEM studies included 572 subjects. The combined PCE was 0.61 (95% CI 0.46-0.80) for acupuncture and 0.69 (95% CI 0.54-0.88) for TEM. CONCLUSION: Our findings suggest that about 61% and 69% of the total treatment effect experienced by subjects receiving acupuncture and TEM treatments, respectively, for knee OA pain may be explained by contextual effects. Contextual effects may include the placebo effect, changes attributable to natural history, and effects of co-therapies. These data highlight the important role of contextual effects in the response to NPNS OA treatments.