Evaluate the efficacy and safety of Hyalgan, at a dose of 20mg/2ml administered as 5 intraarticular injections at weekly intervals, for the sustained relief of pain and amelioration of joint dysfunction in patients of OA of the knee.

Inclusion Criteria:

• 1.Male or female patients whose specific ages are > 50 years old, in general health. 2.Must be ambulatory (assistive devices allowed) 3.Patient was diagnosed as OA of knee joint by American College of Rheumatology (ACR) criteria ; [ ie,knee pain, and any one of the following:age>50 years,crepitus, or morning stiffness<30 minutes in duration ] 4.Radiographic confirmation of OA with Kellgren-Lawrence Ⅱ-Ⅲ score (mild to moderate)at the target joint (anterior-posterior views) with predominance in the tibia-femoral compartment 5.VAS score ≧40 mm for 50 foot of walking pain.

Exclusion Criteria:

• 1.Patients with severe degeneration of knee joint with marked joint narrowing, marked varus or valgus deformity of the knee greater than 12 o. 2.Patients with hepatic or renal failure, or other chronic severe diseases that can interfere with the outcome. 3.A known history of psychiatric diseases, significant neurological diseases, allergy or sensitivity to hyaluronic acid or avian protein. 4.Patients receive steroid intraarticular injection, anti-inflammatory agents less than two weeks. 5.Patients with joint disorders: inflammatory joint disease, specific arthropathy (chondrocalcinosis, joint effusion >30ml), severe axis deviations or instabilities, joint or skin infections, joint prostheses of the lower limbs, symptomatic hip. 6.Significant alcohol, drug or medication abuse as judged by the investigator. 7.Pregnancy determined by clinical evaluation or urine testing for nursing women and/or women of childbearing potential not using a medically approved means of contraception (i.e., oral contraceptives, intrauterine devices, diaphragm or Norplant). 8.Patients who have taken any other "investigational" drug within one month prior to the screening visit.