80 patients with knee osteoarthritis were randomized to one of two treatment groups (a group receiving 2 intra-articular hylan injections vs. a group receiving 3 intra-articular hylan injections) or to one of two control groups (a group receiving 2 placebo injections or a group receiving 3 placebo injections). The purpose of the study was to assess the safety and efficacy of hylan injection therapy, and to compare the differences in injection schedules (2 or 3 injections). Outcomes included rate of treatment success, various VAS scores for pain and function, and global assessment score. Results found a 3 injection hyalin treatment to be significantly more effective than a 2 injection hyalin treatment and both placebo treatments for all outcome measures. A 2 injection treatment was significantly more effective than the placebo treatments for all measures except global assessment and VAS night pain score.