Temporomandibular Joint - Disorders

Disorders

See Temporomandibular joint disorder for more details

The most common disorder of the TMJ is disc displacement. In essence, this is when the articular disc, attached anteriorly to the superior head of the lateral pteygoid muscle and posteriorly to the retrodiscal tissue, moves out from between the condyle and the fossa, so that the mandible and temporal bone contact is made on something other than the articular disc. This, as explained above, is usually very painful, because unlike these adjacent tissues, the central portion of the disc contains no sensory innervation.

In most instances of disorder, the disc is displaced anteriorly upon translation, or the anterior and inferior sliding motion of the condyle forward within the fossa and down the articular eminence. On opening, a "pop" or "click" can sometimes be heard and usually felt also, indicating the condyle is moving back onto the disk, known as "reducing the joint" (disc displacement with reduction). Upon closing, the condyle will slide off the back of the disc, hence another "click" or "pop" at which point the condyle is posterior to the disc. Upon clenching, the condyle compresses the bilaminar area, and the nerves, arteries and veins against the temporal fossa, causing pain and inflammation.

In disc displacement without reduction the disc stays anterior to the condylar head upon opening. Mouth opening is limited and there is no "pop" or "click" sound on opening.

TMJ pain is generally due to one of four reasons.

• The most common cause of TMJ pain is myofascial pain dysfunction syndrome, primarily involving the muscles of mastication.
• Internal derangements is defined as an abnormal relationship of the disc to any of the other components of the TMJ. Disc displacement is an example of internal derangement.
• Degenerative joint disease, otherwise known as osteoarthritis is the organic degeneration of the articular surfaces within the TMJ.
• TMJ pain remains one of the most reliable diagnostic criteria for temporal arteritis.

Although rare, other pathologic conditions may affect the TMJ function, causing pain and swelling, as well. These conditions include chondrosarcoma, osteosarcoma, giant cell tumor and aneurysmal bone cyst.