Objectives. - In a previous study, we determined the costs over 6 months to the French public health insurance system of Hylan GF-20 (Synvisc^®) in 66 patients with knee osteoarthritis. Here, we compared the medicoeconomic benefits over 9 months in 506 patients given Hylan GF-20 or conventional treatment for knee osteoarthritis.

Patients and methods. - This prospective randomized study was conducted from October 1998 to February 2000. Clinical status was evaluated using the Lequesne index, the WOMAC index, and the SF12 quality-of-life questionnaire. Medical and sick leave costs to the public health insurance system were determined.

Results. - Effectiveness criteria were evaluable in all 506 patients. Significant clinical improvements were noted from the first month to the end of the 9-month study period in the Synvisc^® group. A mean 2-point difference in the Lequesne index area-under-the-curve was found in favor of Synvisc^® (P < 0.0001). Mean medical and sick leave costs per patient over 9 months were 829.10 in the Synvisc^® group and 829.40 in the conventional treatment group.

Conclusion. - This study carried out over 9 months in a large population confirms that Synvisc^® viscosupplementation is more effective than conventional treatment, at no additional cost. It takes a step toward answering the request of international experts for medicoeconomic data on viscosupplementation for osteoarthritis.