This Phase II clinical study is to evaluate the efficacy and safety of DA-5202 in patients with osteoarthritis of the knee.

Eligible subjects are randomly assigned to receive DA-5202 high dose(20mg) or DA-5202 low dose(10mg) or Na Hyaluronate once a week intra-articular injection for 3 weeks.

Inclusion Criteria:

• male and female patients between 20 and 80 y old

• primary knee osteoarthritis confirmed clinically and radiologically according to American College of Rheumatology criteria and have following 3 items

  1. knee joint pain

  2. have any of the following

     1. males and females more than 50 y
     2. morning stiffness within 30 minutes
     3. crepitus

  3. presence of spur on radiological evidence

• Kellgren-Lawrence Grade Ⅰ to Ⅲ confirmed radiologically

• knee pain under weight-bearing greater than 40/100mm-VAS(Visual Analogue Scale) at randomization visit

• patients willing and able to provide signed informed consent after the nature of the study has been explained

Exclusion Criteria:

• BMI(Body Mass Index) > 32
• complete obliteration of femoropatellar joint space on X-ray
• Kellgren-Lawrence Grade IV
• knee surgery within a year
• history of fracture, rheumatoid arthritis or other inflammatory arthritis in knee articular cavity
• intra-articular corticosteroid injection within 3 months or hyaluronate injection within 6 months
• skin diseases or infection overlying the joint
• history of severe drug allergy or hypersensitivity to drugs(piroxicam, hyaluronic acid)
• history of allergy, asthma, rhinitis, angioedema, rash to aspirin or other NSAIDs (including COX-2 inhibitor)
• treatment with anticoagulants such as heparin or coumarins (warfarin etc.)
• History of GI diseases such as peptic ulcer, bleeding, perforation, ulcerative colitis, Crohn's disease within 1 year
• severe hypertension
• patients with psychiatric disorder, alcoholism, drug addiction
• presence of severe concomitant diseases or malignancy within 5 years
• have participated in another clinical trial 4 weeks prior to the study
• women of child-bearing potential who are not using *adequate means of contraception (*adequate means of contraception: condom, oral contraception, barrier methods using spermicide, intrauterine devices etc.)
• any condition that, in the view of the investigator, would interfere with study participation