In the treatment of pyogenic artritis, broad spectrum antibiotics contributed to the prevention of joint damage. Many complications, however, result form inadequate treatment, such as I) increasing number of organisms that are resistant to antibiotics used, II) late treatment due to differential diagnosis between pyogenic arthritis and cellulitis and III) antibiotics abuse. We studied 25 cases of pyogenic arthritis of the knee with paying attention to age, sex, duration of mobidity, primary etiology, microbilogic examination and treatment method form February 1983 to Ferbuary 1990 at InJe University, Baik Hospital Busan, Department of Orthopedic Surgery. The results were as follows; 1. The patients consisted of 16 male (64%) 9 female (36%), with 8 cases(3%) below 10 years and 9 cases (36%) above 51 years old. 2. The most common underlyin cause was previous trauma (6 cases, 24%) of which intraarticular steroid injection was 3 cases (12%), and URI in 3 cases (12%) 3. On admission, 15cases (60%) were increased ESR with leukocytosis. 4. The most common organism was staphylococcus aureus (11 cases, 44%) 5. 5 cases (20%) were treated by conservative method, 10 cases (40%) by continuuous irrigation and 8 cases (32%) by arthrotomy and continuous irrigation.