Inclusion Criteria:  Age of 20-85 years Symptomatic knee osteoarthritis for more than 6 months despite analgesics, NSAIDs, or physical therapy Kellgren-Lawrence grade-2 knee osteoarthritis seen on radiographs made within previous 6 months Radiological evidence of bilateral knee OA was accepted if global pain VAS in the contralateral knee was less than 30 mm.  Exclusion Criteria:  Previous orthopedic surgery on spine or lower limb Disabling osteoarthritis of either hip or foot Knee instability, apparent joint effusion, or marked valgus/varus deformity Known allergy to avian proteins or hyaluronan products Confirmed or suspected pregnancy, or lactating Intra-articular injections into knee in previous 6 months Any specific medical conditions (rheumatoid arthritis, active infection, hemiparesis, neoplasm, hematological etc.) that would interfere with assessments