20 patients with Kellgren-Lawrence grade II-III knee osteoarthritis were randomized to either a single intraarticular injection of combined sodium hyaluronate plus mannitol or no injection. Patients were assessed for outcome related to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain, Stiffness, and Function scale, daily rescue diclofenac consumption, and adverse events over 24-week follow-up. Results demonstrated significant favourable results of the HA plus mannitol group compared to the control group for WOMAC Pain up to 20 weeks, WOMAC Stiffness up to 12 weeks, and WOMAC Function up to 16 weeks, as well as diclofenac consumption over the duration of the study. WOMAC Pain, Stiffness, and Function scores at 24 weeks did not significantly differ between groups, however.