Objectives Our objective was to assess the effects of intra-articular injections of hyaluronic acid (HA) (Hylan G-F 20: Synvisc) on symptoms and functional outcome of knee osteoarthritis (OA).

Methods A total of 60 injections were performed in 17 patients involving 20 knees. These patients with symptomatic, radiological knee OA were randomly assigned to treatment with HA or placebo. Treatment group consisted of 12 patients received three weekly injections of HA into one or both (if bilateral symptomatic) knees (15 knees total). Control group consisted of 5 patients who received three intra-articular injections of 2-ml physiological saline with weekly intervals (5 knees total). Fifteen-minute walking period, range of motion, need of drug and painless walking time were noted at weeks 1,2,3,8. Pain at walking, resting, night and motion were evaluated by Visual Analogue Scale (VAS). Also, WOMAC Osteoarthritis Indexes (Pain by WOMAC-A, stiffness by WOMAC-B, activities of daily living by WOMAC-C) were evaluated by Likert scales in the same weekly intervals.

Results Statistically significant improvements (p < 0.001) in WOMAC-A-3 (3rd week), WOMAC-A-8(8th week), WOMAC-B-3, WOMAC-B-8, VAS walking-2,3,8, VAS resting?8, VAS motion-2,3,8, painless walking time-8,15 min walking period-8, need of drug-2,3,8 were found.

When compared with control group, statistically significant improvement was noted (p < 0.05) at WOMAC-A-8, WOMAC-C-8, VAS walking-8, VAS resting ?3,8 painless walking time-2,3,8, need of drug-8. No side effect was encountered in both of the groups.

Conclusion Early signs of efficacy of intra-articular injections of HA for knee OA was beginning in the 2nd week. But this early improvement is not significant when compared with control group. The real effects of the HA treatment were seen at the 8th week. It is concluded that Hylan G-F 20 provided good clinical benefit for knee OA patients and the clinical improvement was prominent after 8 weeks.