The mid-term efficacy of intra-articular hyaluronic acid injections on joint structure: a nested case control study

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.

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.

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.

IA-HA might effectively improve joint structure and relieve pain in patients with knee OA.