Objectives. - To describe the long-term effects of Hylan GF-20 viscosupplementation in patients with knee osteoarthritis and to identify factors predicting efficacy.

Methods. - One hundred and fifty-five patients (80 women and 75 men; mean age, 69 years) with symptomatic knee osteoarthritis each received three intraarticular Hylan GF-20 injections. Effectiveness, safety, and satisfaction were evaluated 7-14 months later based on a physician's examination and a five-item questionnaire. Radiological data (distribution and degree of joint space loss), size of the effusion (none, moderate, large), injection route (anterior, medial to the patella, or lateral to the patellar), and side effects were recorded. Factors predicting effectiveness were looked for by univariate analysis followed by multivariable analysis with adjustments on age, body mass index, gender, and time from treatment to questionnaire administration.

Results. - Satisfaction was good in 78% and 58.9% of the patients according to the physician examination and questionnaire, respectively. Safety was considered excellent or good in 96.2% of the patients. Factors significantly (P < 0.05) associated with a good outcome were a moderate effusion, injection lateral to the patella, joint space loss in a single compartment, and radiological meniscal calcinosis.

Conclusion. - The factors predictive of a good response to Hylan GF-20 in this study need to be confirmed, and their impact quantitated, in prospective studies.