We report a case of calcium pyrophosphate dehydrate crystal deposition with synovial chondromatosis and calcification of the articular disc in the temporomandibular joint （TMJ）. A 59-year-old-woman was referred to our hospital because of pain in the left TMJ and difficulty in opening and closing her mouth. The first clinical examination revealed that her maximal mouth opening was 18 mm, with open bite at the left molars. Radiological examination revealed a calcified mass in the left TMJ. The clinical diagnosis was synovial chondromatosis. Since arthroscopy showed no abnormal findings in the upper joint space, we tried to open the lower joint space. During surgery, we found a whitish-yellow mass on the lateral side of the capsule. When the lower joint space was opened, two loose solid masses were found in the anterior space. The lower surface of the disc was found to be calcified, and considerable white-yellow deposition was found in its posterior space. The disk, the loose masses, and the deposition were removed. Histological examination showed calcium pyrophosphate dehydrate crystal deposition, chondromatosis, and calcification of the disc. Three years 6 months postoperatively, the patient was found to be free of symptoms, without relapse.
