Synovial chondromatosis with cranial extension.

Synovial chondromatosis is a benign arthropathy characterized by metaplasia in synovial membranes that can produce detached particles of cartilage. It occurs most often in the knee, hip, and elbow but has been reported in the temporomandibular joint. This is a rare presentation of synovial chondromatosis with glenoid fossa erosion and cranial extension.