Effects of Transcranial Direct Current Stimulation and Individualized Physical Therapy on Pain and Function in Individuals With Chronic Knee Pain: A Pilot Study.

Abstract

BACKGROUND AND PURPOSE: Noninvasive brain stimulation is a promising neuromodulatory intervention for chronic pain. This study aimed to determine the impact that transcranial direct current stimulation (tDCS) in combination with individualized physical therapy (PT) has on pain and function in individuals with chronic knee pain. METHODS: This study was a preliminary pragmatic, triple-blinded, randomized, and sham-controlled clinical trial performed in an outpatient orthopedic physical therapy clinic. Participants participated in 5 sessions of active or sham tDCS followed by individualized PT intervention. Pain outcomes included the Numeric Pain Rating Scale, Movement-Evoked Pain, pressure pain thresholds (PPT), and the Central Sensitization Inventory. Functional outcomes included the 2-minute walk test, 5-time sit-to-stand test, quadriceps strength, knee range of motion, Patient Specific Functional Scale, and the Lower Extremity Functional Scale. RESULTS: Thirty participants with chronic knee pain completed the study. There were no significant differences observed for primary patient-centered pain and functional outcomes. For secondary outcomes, the active tDCS group had a significant effect (p&#xa0;<&#xa0;0.05) on percent change in lateral joint line PPT and a significant multivariate effect of group on PPT change scores for 3-site and 5-site clusters (p&#xa0;<&#xa0;0.05). Exploratory responder analyses demonstrated that the active tDCS group was 12.8 times more likely to achieve the minimum detectable change in quadriceps strength improvement compared with the sham tDCS group (p&#xa0;<&#xa0;0.05). DISCUSSION: There were no significant between-group differences for primary pain and functional outcomes. However, the active tDCS group showed improvements in pain sensitivity, as measured by PPT, and quadriceps strength, which were superior to those seen in the sham tDCS group. These preliminary findings provide insight into possible mechanisms of tDCS in addressing pain as opposed to efficacy. Given that there were no clear between-group differences in patient-centered outcomes, there is insufficient evidence for routine tDCS use for chronic knee pain. TRIAL REGISTRATION: NCT06132412.