Effects of transcranial direct current stimulation on pain and function in patients with knee osteoarthritis: A systematic review and meta-analysis.

The meta-analysis included only 7 trials, so the pooled estimates rest on a limited number of studies. The trials used different tDCS doses and schedules, including 5, 10, 15, 16, or 30 sessions, and the review could not compare different durations or doses because there were not enough studies. Some trials combined tDCS with other treatments, including therapeutic exercise, transcutaneous electrical nerve stimulation or electrical intramuscular stimulation, meditation, or conventional physiotherapy, so the contribution of tDCS alone cannot be assumed. Blinding of the outcome assessor was the most frequently observed bias. The certainty of evidence for function was low because the WOMAC reflects self-reported function rather than objectively tested performance. Conditioned pain modulation showed no significant difference and had substantial heterogeneity, so the review does not show an effect on endogenous pain inhibition. The included adults had at least moderate knee osteoarthritis and no comorbidities that could affect knee function or pain, so the results may not apply to patients with more complex problems. The studies by Ahn et al. had substantial influence on the overall results and conclusions.

This work was supported in part by the Spanish Government and the European Union European Regional Development Fund under grant PID2021-125694OB-I00, and by Generalitat Valenciana under CIAICO/2024/107. The funding information also names Ministerio de Ciencia e Innovación. The authors declared no conflict of interest.

Do not conclude that tDCS alone reliably improves knee osteoarthritis pain or function. Several trials added other treatments, such as therapeutic exercise, transcutaneous electrical nerve stimulation or electrical intramuscular stimulation, meditation, or conventional physiotherapy, and the review did not show that tDCS alone is responsible for all reported improvements. The function result was also rated low certainty.