80 patients with Kellgren-Lawrence grade II-IV knee osteoarthritis were randomized to a course of five weekly intraarticular injections of either low molecular weight hyaluronic acid or high molecular weight hyaluronic acid. Patients were assessed for response the therapy in a visual analog scale for pain, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and medial and lateral joint space width on radiograph. No significant differences between groups were noted in any of the assessed outcome measures at 5 weeks, 3 months, or 1 year following treatment.