Synovial chondromatosis is a rare monarticular condition in which cartilaginous masses are formed by metaplasia of the synovial membrane. These masses may calcify and ossify. The disease most commonly affects the knee, and the symptoms include pain, swelling, locking and palpable loose bodies. Although the clinical features are usually non-specific, the roentgenograms often provide important diagnostic information. Synovial chondromatosis is rarely a difficult diagnostic problem, but should not be confused with other disorders that give rise to loose bodies, such as degenerative joint disease and osteochondritis dissecans. Two cases are described and synovial chondromatosis is discussed in some detail, including radiological features and treatment.