Objective: Intra-articular (IA) injection of hyaluronic acid (HA) has been shown to relieve osteoarthritis (OA)-related pain and improve joint structure within a 1-year period. We examined the mid-term (2-year) efficacy of IA-HA in Japanese subjects by using a large-scale population-based cohort of the Research on Osteoarthritis/Osteoporosis Against Disability study.
Methods: We performed a nested case control study of 60 case control pairs matched for age (within 1 year), sex, Kellgren and Lawrence grade, and history of knee pain. The mean follow-up period after IA-HA series was 2.9 years in case patients. We examined the association of IA-HA with knee radiographic severity and knee pain. To estimate radiographic severity of OA, six distinct features--joint space area and the minimum joint space width at medial and lateral sides, osteophyte area, and tibiofemoral angle--were measured using a fully automatic computer-assisted program.
Results: Comparison of the radiographic parameters between case patients and controls showed that the medial and lateral joint space areas were significantly bigger in case patients than in controls. After constructing a multivariate logistic regression model to examine the correlation of knee pain, IA-HA, and radiographic features, we found that unlike radiographic features, IA-HA was protectively associated with the presence of pain.
Conclusion: IA-HA might effectively improve joint structure and relieve pain in patients with knee OA.