Exploring whether home-based neuromodulation can boost the analgesic effects of exercise in people with knee osteoarthritis: protocol for a double-blinded, pilot randomised controlled trial.

Introduction: Knee osteoarthritis (OA) represents a leading cause of disability globally. Exercise has been demonstrated to improve pain and function in people with knee OA. However, when in pain, commencement of exercise is difficult, and clinical effects with such interventions are often modest. Recently, transcranial direct current stimulation (tDCS), a form of non-invasive brain stimulation, has been shown to bolster the pain-relieving effect of exercise in experimental settings. While promising, the utility of employing this approach beyond the research environment is yet to be elucidated. Therefore, this pilot study aims to investigate the feasibility, safety, adherence, tolerability and preliminary efficacy of tDCS and exercise in home-based settings to improve pain and function in people with knee OA.

Methods and analysis: This protocol is for a pilot randomised, double-blinded, sham-controlled trial. 24 individuals with idiopathic knee OA will be randomised to receive either active tDCS+exercise (Intervention) or sham tDCS+exercise (Control) at home. Participants will receive 20 min of tDCS 5 days per week for the first 2 weeks of this 8-week trial. Participants in both groups will complete a lower limb strengthening programme 3 days per week for the entire 8 weeks. Outcome measures of feasibility (acceptability, satisfaction, retention), safety, adherence and tolerability will be assessed throughout the trial period, with clinical outcomes of pain and function assessed before and following the intervention. Feasibility, safety, adherence and tolerability outcomes will be explored descriptively using frequencies and percentages. To examine preliminary efficacy, within-group and between-group changes in pain and functional measures will be analysed.

Ethics and dissemination: This protocol obtained ethical approval from the Queensland University of Technology Human Research Ethics Committee (HREA 2024-8302-20200). All participants will provide written informed consent. The findings of the study will be disseminated via journal publications and international conference proceedings.

Trial registration number: ACTRN12624000397516p.