Thirty patients with chronic idiopathic knee osteoarthritis (Larsen grade II or III) were randomized to receive three once-weekly intra-articular injections of either Hylan G-F 20 (n=15) or placebo (n=15). The primary outcome was pain relief as assessed by visual analogue scale (VAS) scores at weeks 12 and 26. Secondary outcomes included patient activity level, overall clinical condition, and adverse events. Follow-up occurred at multiple intervals up to 26 weeks. Overall, the study revealed that Hylan G-F 20 significantly improved patient-assessed and evaluator-assessed outcomes (p<0.0001), except for night pain and inactivity stiffness, with no significant safety concerns. These findings suggest that Hylan G-F 20 provides effective and sustained pain relief in this population.