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-week 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 weeks with four 20-minute sessions weekly. Twenty-seven participants finished the intervention and a 12-week follow-up (14 and 13 in each group). Assessments using the Visual Analogue Scale (VAS) for pain and the Timed Up and Go (TUG) test for mobility were conducted at week 0 (baseline), week 7 (6-week training), week 11 (4-week detraining), and week 19 (further 8-week detraining). Two-way mixed design ANOVA and a simple mediation model were used for data analysis. Results: Significant time*group interactions were detected in VAS scores (p=0.009, η 2 p =0.391) and TUG times (p=0.011, η 2 p =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 to 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% CI: 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.