Forty-four women with knee osteoarthritis were randomized to receive anodal transcranial direct current stimulation (tDCS) (2 mA, M1, 20 min) followed by aquatic neuromuscular training (ANMT) (n=22) or sham tDCS plus the same ANMT (n=22); at six weeks, analyses included twenty per group. The primary outcome was pain (0–10 NRS) assessed weekly and at six weeks. Secondary outcomes were physical function (WOMAC), self-reported knee instability, kinesiophobia (TSK), and quality of life (OAKHQOL), measured pre- and post-intervention across 18 sessions over six weeks. Overall, the results revealed a significant immediate (week-by-week) pain advantage for real tDCS (group×time p<0.001, η²p=0.35), but no between-group difference in pain at six weeks (p=0.36, η²p=0.02). Importantly, at six weeks real tDCS produced greater gains in knee instability (interaction p=0.04, η²p=0.10) and function (WOMAC interaction p=0.03, η²p=0.10), with no between-group differences for kinesiophobia or quality of life. These findings suggest pairing anodal tDCS with ANMT accelerates pain relief and yields modest additional benefits in stability and function, though pain levels converge by six weeks.