Efficacy of low frequency pulsed subsensory threshold electrical stimulation vs placebo on pain and physical function in people with knee osteoarthritis: systematic review with meta-analysis

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To determine if low frequency (≤100Hz) pulsed subsensory threshold electrical stimulation produced either through pulsed electromagnetic field (PEMF) or pulsed electrical stimulation (PES) vs sham PEMF/PES intervention is effective in improving pain and physical function at treatment completion in adults with knee osteoarthritis (OA) blinded to treatment. The relevant studies were identified by searching eight electronic databases and hand search of the past systematic reviews on the same topic till April 5, 2012. We included randomized controlled trials (RCTs) of people with knee OA comparing the outcomes of interest for those receiving PEMF/PES with those receiving sham PEMF/PES. Two reviewers independently selected studies, extracted relevant data and assessed quality. Pooled analyses were conducted using inverse-variance random effects models and standardized mean difference (SMD) for the primary outcomes. Seven small trials (459 participants/knees) were included. PEMF/PES improves physical function (SMD=0.22, 95% confidence interval (CI)=0.04, 0.41, P=0.02, I(2)=0%), and does not reduce pain (SMD=0.08, 95% CI=-0.17, 0.32, P=0.55, I(2)=43%). The strength of the body of evidence was low for physical function and very low for pain. Current evidence of low and very low quality suggests that low frequency (≤100Hz) pulsed subsensory threshold electrical stimulation produced either through PEMF/PES vs sham PEMF/PES is effective in improving physical function but not pain intensity at treatment completion in adults with knee OA blinded to treatment. Methodologically rigorous and adequately powered RCTs are needed to confirm the findings of this review.