To confirm the pathophysiology and proper treatment of synovial chondromatosis according to preoperative radiographs, intraoperative findings, and postoperative histology.

Twenty one patients with synovial chondromatosis who underwent the removal of loose bodies and synovectomy since 1995 were investigated. Patients were analyzed in terms of various radiologic and histologic findings of osteochondromas and synovium.

The joints involved were the shoulder joint in 9, the knee in 7, the hip in 3, and the elbow in 2 patients. Removals of osteochondromas were performed in all patients, and four who had intrasynovial proliferating nodules were treated by partial synovectomy. Histologically, the synovia were hypertrophied, and osteochondromas classifiable as three distinct types: premature, maturing, and matured. Osteochondromas in the synovium were of the premature type. There were no recurrences at an average 39 months of follow-up.

Based on a study of 21 cases of synovial chondromatosis, there appear to be three separate types of this disease: premature, maturing, and matured. Partial synovectomy may be necessary in premature and maturing types with intrasynovial proliferating nodules.