We recently experienced a case of degenerative disease of the temporomandibular joint. A healthy, 12-year-old female with bilateral high maxillary canines presented for orthodontic treatment. Two years after active orthodontic treatment, at the age of 17 years old, symptoms in her temporomandibular joint manifested and progressed. By the time she revisited our hospital at age 21, the patient had developed anterior open bite with a long, slender facial appearance. Cephalometric analysis showed shortening of the ramus and backward and downward rotation of the mandible. Imaging studies revealed severe deformity and resorption of the bilateral condyles. Her occlusal and morphological changes seemed to be caused by degenerative disease of the temporomandibular joint.