Effectiveness of transcranial direct current stimulation in knee osteoarthritis: A systematic review and meta-analysis of randomized sham-controlled trials

Objective Assess the effectiveness of transcranial direct current stimulation (tDCS) in knee osteoarthritis (OA). Methods Searched PubMed, Cochrane Library, Embase, and Scopus databases until August 3, 2023, and identified randomized controlled trials (RCTs) evaluating the effects of tDCS in knee OA whose outcomes using pain scores or functional scales. The selected RCTs were subjected to meta-analysis and risk of bias assessment. Results Seven RCTs involving 488 patients were included in this meta-analysis. Compared with the control group, the tDCS group exhibited significant improvement in pain scores after treatment (standardized mean difference [SMD] = 1.03; 95% confidence interval [CI]: 0.70 to 1.35; n = 359; I2 = 46%), pain scores during follow-up (SMD = 0.83; 95% CI: 0.21 to 1.45; n = 358; I2 = 86%), and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores after treatment (SMD = 4.76; 95% CI: 0.16 to 9.53; n = 319; I2 = 74%), but WOMAC scores during follow-up did not differ significantly between the groups (SMD = 0.06; 95% CI: -0.2 to 0.32; n = 225; I2 = 0%). Conclusion tDCS is a promising therapy for knee OA. Further investigation using large-scale, high-quality RCTs is necessary for optimal tDCS approach in knee OA.