51 patients with knee osteoarthritis were randomized to intraarticular therapy with either platelet-rich plasma alone, platelet-rich plasma combined with low-molecular-weight hyaluronic acid, or platelet-rich plasma combined with high-molecular-weight hyaluronic acid. Patients were assessed for outcome on the International Knee Documentation Committee (IKDC) score and visual analog scale (VAS) pain after 6 weeks and 6 months. Results demonstrated no significant between-groups differences between any two of the three groups for either outcome measure at 6 weeks or 6 months.