32 patients with Kellgren Lawrence grade II-IV knee osteoarthritis were randomized to a single intraarticular injection of either high molecular weight hyaluronic acid (Hylan G-F 20; Genzyme) or low molecular weight hyaluronic acid (Hyalgan). Patients were assessed for response on a visual analog scale for pain during walking, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the Short Form 36-Item Health Survey (SF-36). Results demonstrated no significant between-group differences for any of the assessed outcome measures.