Objective: To study the efficacy of 0.0125% capsaicin patch at acupuncture point for pain relief in knee osteoarthritis (OA). Methods: This randomized, double-blind, placebo-controlled clinical trial was conducted during September 2014 to March 2015. Sixty-two ambulatory patients over 50 years of age with a diagnosis of knee OA were included. All enrolled patients had a pain score of 4-7 out of 10. Participants were randomized into either the treatment (capsaicin, n=31) or control (placebo, n=31) group.

Interventions: Capsaicin vs. placebo patch at ST34 (1), SP10 (2), ST35 (3), EX-LE4 (Neixiyan) (4), ST36 (5), and SP9 (6) acupuncture points for 4 weeks. Main outcome measure: Pain subscale of modified Thai version of Western Ontario and McMaster (WOMAC) Osteoarthritis Index was assessed at baseline, 2, 4, 6, and 8 weeks after treatment.

Results: Pain subscale of modified Thai version of WOMAC showed no significant difference between groups at baseline, 2, 4, 6, and 8 weeks after treatment. After 2 weeks of treatment, the pain subscale score in the treatment group was significantly decreased from baseline (p<0.001). After 4 weeks of treatment, the pain subscale score in the placebo group was significantly decreased from baseline (p<0.006).

Conclusion: Capsaicin patch at acupuncture point for pain relief in knee OA yielded no significant difference between groups. However, significant pain relief from baseline was observed in the treatment group after 2 weeks of treatment and in the placebo group after 4 weeks of treatment. Further study with higher capsaicin concentration and/or larger size patch should be considered.