In a prospective, randomized controlled, double-blind trial with 6-month follow up, patients with knee OA (Kellgren-Lawrence grade 2 or 3) were randomized to receive one intraarticular injection of 3 ml HYAJOINT Plus (microbial fermented HA, 20 mg/ml) (N=66) or 6 ml Synvisc-One (avian derived HA, 8 mg/ml) (N=66). The primary outcome was change in the visual analog scale (VAS) pain (0-100mm) over 6 months. Secondary outcomes included The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne index, Timed Up-and-Go test (TUG), single leg stance test (SLS), use of rescue analgesics and patient satisfaction.