Transcranial Direct Current Stimulation Improves the Overall Pain Experience of Older Adults with Knee Osteoarthritis

Objective: Chronic pain in osteoarthritis (OA) is a multidimensional phenomenon requiring thorough assessment and appropriate treatment. Here, we assessed the impact of home-based, remotely supervised transcranial direct current stimulation (tDCS) on the overall pain experience of older adults with knee OA by simultaneously examining its effects on multiple pain domains—pain intensity, pain interference, and pain catastrophizing—using multi-group latent transition analysis (LTA). Methods: This secondary analysis of a randomized clinical trial involved 120 participants with knee OA-associated pain assigned to undergo 15 daily sessions of active 2-mA tDCS ( n = 60) or sham stimulation ( n = 60) over 3 weeks via telehealth. Pain intensity, pain interference, and pain catastrophizing were measured at baseline and at the end of weeks 1, 2, and 3 (after five sessions each). Multi-group LTA enabled the simultaneous measurement of multiple pain domains and analysis of their changes as a function of intervention exposure by modeling the transition probabilities of latent classes and comparing these changes between the groups. Results: Three latent categories were identified based on three pain domains: “high pain,” “moderate pain,” and “low pain.” Active group participants with “moderate pain” at baseline had 24.2% probability of transitioning to “low pain” after week 1, whereas sham group participants remained stagnant during this interval. Notably, 37.6% of active group participants with “high pain” at week 1 transitioned to “moderate pain,” while 35.8% of those with “moderate pain” at week 1 transitioned to “low pain” by week 2 (after an additional five sessions). Nevertheless, no noticeable changes were observed in the sham group during this period. No pronounced intervention effects were noted by week 3. Conclusions: Simultaneously modeling pain-related measures enriches our understanding of the efficacy of tDCS in improving the overall pain experience among older adults with knee OA.