Longitudinal associations between complementary and alternative medicine use and pain trajectories in knee osteoarthritis: a panel analysis from the Osteoarthritis Initiative.

OBJECTIVE: This study aimed to investigate longitudinal changes in knee pain and function according to complementary and alternative medicine (CAM) use, with a particular focus on acupuncture and chiropractic therapy, among patients with knee osteoarthritis (KOA). METHODS: We analyzed data from the Osteoarthritis Initiative, a large longitudinal cohort of patients with KOA. CAM use, including acupuncture and chiropractic therapy, was assessed at baseline and at 2, 4, and 8 years. Changes in knee pain and physical function were measured using the numeric rating scale (NRS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Random-effects panel regression models were used to evaluate the longitudinal associations between CAM use and outcome changes. RESULTS: Among the 3,838 participants included in the final analysis, approximately 10% reported CAM use at each visit. CAM use was significantly associated with reductions in knee pain over time (β = -0.34, p = 0.007). In modality-specific analyses, chiropractic therapy was significantly associated with pain reduction (β = -0.41, p = 0.005), whereas acupuncture showed a non-significant association with pain improvement. CAM use was not significantly associated with changes in the WOMAC scores. The combined use of acupuncture and chiropractic showed a greater, but non-significant, reduction in pain compared with single-modality use. CONCLUSIONS: CAM use, particularly chiropractic therapy, was associated with a small but statistically significant reduction in knee pain in patients with KOA. Given the modest effect size and observational design, these findings warrant further prospective evaluation of chiropractic care as a non-pharmacological option.