(See also Overview of Temporomandibular Disorders.)
Ankylosis of the temporomandibular joint (TMJ) most often results from trauma or infection, but it may be congenital or a result of rheumatoid arthritis. Chronic, painless limitation of mandibular motion occurs. When ankylosis leads to arrest of condylar growth, facial asymmetry is common (see Mandibular Condylar Hyperplasia).
Intra-articular (true) ankylosis must be distinguished from extra-articular (false) ankylosis, which may be caused by enlargement of the coronoid process, depressed fracture of the zygomatic arch, or scarring resulting from surgery, irradiation, or infection. In most cases of true ankylosis, x-rays of the joint show loss of normal bony architecture.
Treatment may include a condylectomy if the ankylosis is intra-articular or an ostectomy of part of the ramus if the coronoid process and zygomatic arch are also affected. Jaw-opening exercises must be done for months to years to maintain the surgical correction, but forced opening of the jaws without surgery is generally not indicated and is usually ineffective because of bony fusion.