70 patients, 18 years of age or older, with knee osteoarthritis were randomized to three weekly intraarticular injections of either high molecular weight hyaluronic acid or low molecular weight hyaluronic acid. Patients were assessed of outcome, primarily related to pain and treatment response, on visual analog scales. Both patient- and evaluator-rated assessments were completed. For weight-bearing pain, improvement from baseline to 12 weeks was significant greater in the HMW HA group, as judged by both patients and evaluators. For treatment response, scores at 12 weeks were significantly greater in the HMW HA group, as judged as both patients and evaluators.