78 patients with a confirmed diagnosis of knee osteoarthritis were randomized to receive intra-articular injections of either a hyaluronan product (Orthovisc), a high-molecular-weight hyaluronan product (Synvisc), or placebo, weekly. The purpose of the study was to compare the efficacy of these different formulations of hyaluronic acid. The results of this study indicated improvements in pain, function and global assessments for all three groups; however, the hyaluronic acid groups were not clinically superior to the placebo treatment 6 months after treatment initiation for pain and there were no differences between the hyaluronic acid preparations.