Synergistic Effects of Joint-Biased Rehabilitation and Combined Transcranial Direct Current Stimulation (tDCS) in Chronic Ankle Instability: A Single-Blind, Three-Armed Randomized Controlled Trial

<b>Background/Objectives:</b> The ankle joint is among the most frequently injured joints in daily life, with approximately 25% of young adults reporting chronic ankle instability (CAI). This study investigated the effects of transcranial direct current stimulation (tDCS), a type of non-invasive brain stimulation (NIBS) technique, combined with joint mobilization and active joint mobilization on CAI. <b>Methods:</b> A total of 36 participants (mean age: 20.81 years; 63.89% female; mean body mass index: 21.68) were randomly divided into three groups: (1) tDCS with joint mobilization (<i>n</i> = 12); (2) active joint mobilization (<i>n</i> = 12); and (3) tDCS with active joint mobilization (<i>n</i> = 12). Dynamic balance, range of motion (ROM), static balance, and ankle instability (Cumberland Ankle Instability Tool, CAIT) were evaluated at multiple time points. Interventions were conducted three times per week, for 15 min per session, over four weeks (12 sessions total). <b>Results:</b> All three groups showed significant improvements over time in dynamic balance, ankle instability, ROM, and static balance (<i>p</i> < 0.05). However, no significant interaction effects were observed between time and group (<i>p</i> > 0.05). The tDCS with active joint mobilization group demonstrated the largest effect sizes across most outcome measures, particularly for ankle instability, ROM, and static balance, in both immediate and post-intervention assessments. <b>Conclusions:</b> tDCS combined with active joint mobilization appears to be particularly effective in improving CAI. This approach, targeting both top-down mechanisms through non-invasive brain stimulation and local joint function, offers a promising alternative to traditional interventions that focus solely on the ankle joint. This study was registered with the Clinical Research Information Service (CRIS) under the identifier KCT0009566.