Study to Evaluate the Efficacy and Safety of Intra-articular DA-5202 in Patients With Osteoarthritis of the Knee

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