Efficacy and Sustainability of tDCS Combined with TENS in Alleviating Pain and Improving Functional Mobility in Older Adults with Knee Osteoarthritis

PURPOSE: This study evaluated the effectiveness and sustainability of a 6-wk intervention combining transcranial direct current stimulation (tDCS) and transcutaneous electrical nerve stimulation (TENS) for pain and functional mobility in older adults with knee osteoarthritis (KOA). It also explored the mediation effect of pain relief on functional mobility. METHODS: Thirty older adults with KOA were randomly split into tDCS + TENS and TENS groups in a 1:1 ratio. The former received combined tDCS and TENS, while the latter had TENS with sham tDCS, for 6 wk with four 20-min sessions weekly. Twenty-seven participants finished the intervention and a 12-wk follow-up (14 and 13 in each group). Assessments using the visual analog scale (VAS) for pain and the Timed Up and Go (TUG) test for mobility were conducted at week 0 (baseline), week 7 (6-wk training), week 11 (4-wk detraining), and week 19 (further 8-wk detraining). Two-way mixed-design analysis of variance and a simple mediation model were used for data analysis. RESULTS: Significant time × group interactions were detected in VAS scores ( P = 0.009, ηp2 = 0.391) and TUG times ( P = 0.011, ηp2 = 0.397). The tDCS + TENS group showed lower VAS scores at weeks 7, 11, and 19, and lower TUG times at weeks 7 and 11 compared with week 0. The TENS group had lower scores and times at weeks 7 and 11. A significant mediation effect of pain scores on TUG times was seen in the TENS group (95% confidence interval: 0.008-0.406). CONCLUSIONS: The combination of tDCS and TENS demonstrates superior and more enduring efficacy in alleviating pain and enhancing functional mobility in older adults with KOA. TENS improves functional mobility primarily through pain reduction, while the tDCS + TENS intervention likely operates via other mechanisms.