A one-year study found that injections of a new hyaluronic acid compound called NRD101 have the same effect on osteoarthritis of the knee as placebo, or “dummy,” injections do, French researchers report.

Hyaluronic acid is thought to restore elasticity to the synovial fluid that surrounds the knee joint, which is depleted in patients with osteoarthritis of the knee. However, the effectiveness of this approach is unproven, Dr. Maxime Dougados of Cochin Hospital in Paris and colleagues report in the December issue of the Annals of the Rheumatic Diseases.

The researchers therefore compared the safety and effectiveness of NRD101 with an orally administered drug, diacerein, shown by past research to have a structural benefit in hip osteoarthritis.

Three hundred one patients were randomly assigned to receive three courses of NRD101 injections, each involving one injection weekly for three weeks, every three months, along with a placebo capsule; placebo injections and diacerein twice daily; or placebo injections and capsules.

Symptoms were evaluated both by patients and clinicians, and X-rays were performed to evaluate the effects of treatment on the knee structure at the beginning and end of the study.

Patients in all three groups reported improvement of their symptoms, but a small degree of structural deterioration occurred in each group. The improvement was most likely due to a “huge placebo effect” related to the injections, Dougados told Reuters Health.

Few patients dropped out of the study, which suggests injections are a feasible approach to treating knee osteoarthritis, Dr. Dougados said. Further studies are needed to evaluate other treatment approaches using this route of administration.

SOURCE: Annals of Rheumatic Diseases, December 2004.