Combined exercise and transcranial direct current stimulation intervention for knee osteoarthritis: protocol for a pilot randomised controlled trial

Introduction: Osteoarthritis (OA) is a major health problem and a leading cause of disability. The knee joint is commonly affected, resulting in pain and physical dysfunction. Exercise is considered the cornerstone of conservative management, yet meta-analyses indicate, at best, moderate effect sizes. Treatments that bolster the effects of exercise, such as transcranial direct current stimulation (tDCS), may improve outcomes in knee OA. The aims of this pilot study are to (1) determine the feasibility, safety and perceived patient response to a combined tDCS and exercise intervention in knee OA, and (2) provide data to support a sample size calculation for a fully-powered trial should trends of effectiveness be present. Methods and analysis: A pilot randomised, assessor-blind and participant-blind, sham-controlled trial. 20 individuals with knee OA who report a pain score of 40 or more on a 100 mm visual analogue scale on walking, and meet a priori selection criteria will be randomly allocated to receive either: (1) active tDCS plus exercise, or (2) sham tDCS plus exercise. All participants will receive 20 min of either active or sham tDCS immediately prior to 30 min of supervised muscle strengthening exercise twice a week for 8 weeks. Participants in both groups will also complete unsupervised home exercises twice per week. Outcome measures of feasibility, safety, pain, disability and pain system function will be assessed immediately before and after the 8-week intervention. Analyses of feasibility and safety will be performed using descriptive statistics. Statistical analyses will be used to determine trends of effectiveness and will be based on intention-to-treat as well as per protocol. Ethics and dissemination: This study was approved by the institutional ethics committee (H10184). Written informed consent will be obtained from all participants. The results of this study will be submitted for peer-reviewed publication.