Meta-analysis: Acupuncture for osteoarthritis of the knee

Background: Knee osteoarthritis is a major cause of pain and functional limitation. Purpose: To evaluate the effects of acupuncture for treating knee osteoarthritis. Data Sources: Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE databases to January 2007. No language restrictions were applied. Study Selection: Randomized trials longer than 6 weeks in duration that compared needle acupuncture with a sham, usual care, or waiting list control group for patients with knee osteoarthritis. Data Extraction: Two authors independently agreed on eligibility, assessed methodological quality and acupuncture adequacy, and extracted outcome data on pain and function measures. Data Synthesis: Eleven trials met the selection criteria, and 9 reported sufficient data for pooling. Standardized mean differences were calculated by using differences in improvements from baseline between patients assigned to acupuncture and those assigned to control groups. Compared with patients in waiting list control groups, patients who received acupuncture reported clinically relevant short-term improvements in pain (standardized mean difference, -0.96 [95% CI, -1.21 to -0.70]) and function (standardized mean difference, -0.93 [CI, -1.16 to -0.69]). Patients who received acupuncture also reported clinically relevant short- and long-term improvements in pain and function compared with patients in usual care control groups. Compared with a sham control, acupuncture provided clinically irrelevant short-term improvements in pain (standardized mean difference, -0.35 [CI, -0.55 to -0.15]) and function (standardized mean difference, -0.35 [CI, -0.56 to -0.14]) and clinically irrelevant long-term improvements in pain (standardized mean difference, -0.13 [CI, -0.24 to -0.01]) and function (standardized mean difference, -0.14 [CI, -0.26 to -0.03]). Limitation: Sham-controlled trials had heterogeneous results that were probably due to the variability of acupuncture and sham protocols, patient samples, and settings. Conclusions: Sham-controlled trials show clinically irrelevant short-term benefits of acupuncture for treating knee osteoarthritis. Waiting list-controlled trials suggest clinically relevant benefits, some of which may be due to placebo or expectation effects.