110 patients with knee osteoarthritis and effusion were randomized to receive either 4 weekly intra-articular injections of hyalectin, or 4 weekly injections of saline solution. The purpose of the study was to determine the efficacy of hyalectin treatment in terms of effusion reduction, pain, and function, and to identify any safety risks, up to one year after treatment. The primary outcome of interest was number of patients with knee effusion at the end of the short-term follow up (7 weeks). Other outcomes included volume of knee effusion fluid, VAS scores for pain at rest and after exercise, Lequesne functional score, overall physician assessment, and adverse events. Results indicated a short-term benefit of hyalectin treatment for knee effusion rate/volume and pain after exercise, and a long-term benefit (up to one year) for functional outcome. No significant difference in pain at rest was observed between groups. Incidence of adverse events was similar between groups.