The temporomandibular joint (TMJ) is a small joint located in front of the ear where the skull and lower jaw meet. It permits the lower jaw (mandible) to move and function. There are two TMJs, one on either side, working in unison. The unique feature of the TMJs is the articular disk.
The TMJs are one of the only synovial joints in the human body with an articular disk, another being the sternoclavicular joint. The disk divides each joint into two.
TMJ disorders are not uncommon and have a variety of symptoms. Patients may complain of earaches, headaches and limited ability to open their mouth. They may also complain of clicking or grating sounds in the joint and feel pain when opening and closing their mouth. What must be determined, of course, is the cause.
What Causes TMJ Disorders?
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 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 eminance. On opening, a "pop" or "click" can sometimes be heard and usually felt as well, 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". Now 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 three 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.
What are the common symptoms of TMJ disorders?
TMJ pain disorders usually occur because of unbalanced activity of the jaw muscles and/or jaw muscle spasm and overuse. Symptoms tend to be chronic, and treatment is aimed at eliminating precipitating factors. Many symptoms may not appear related to the TMJ itself. The following are common symptoms.
Headache: Approximately 80% of patients with a TMJ disorder complain of headache, and 40% report facial pain. Pain is often made worse while opening and closing the jaw. Exposure to cold weather or air-conditioned air may increase muscle contraction and facial pain.
Ear pain: About 50% of patients with a TMJ disorder notice ear pain but do not have signs of infection. The ear pain is usually described as being in front of or below the ear. Often, patients are treated multiple times for a presumed ear infection, which can often be distinguished from TMJ by an associated hearing loss or ear drainage (which would be expected if there really was an ear infection). Because ear pain occurs so commonly, ear specialists are frequently called on to make the diagnosis of a TMJ disorder.
Sounds: Grinding, crunching, or popping sounds, medically termed crepitus, are common for patients with a TMJ disorder. These sounds may or may not be accompanied by increased pain.
Dizziness: Of patients with a TMJ disorder, 40% report a vague dizziness or imbalance (usually not a spinning type vertigo). The cause of this type of dizziness is not well understood.
Fullness of the ear: About 33% of patients with a TMJ disorder describe muffled, clogged, or full ears. They may notice ear fullness and pain during airplane takeoffs and landings. These symptoms are usually caused by Eustachian tube dysfunction, the structure responsible for the regulation of pressure in the middle ear. It is thought that patients with TMJ disorders have hyperactivity (spasms) of the muscles responsible for regulating the opening and closing of the Eustachian tube.
Ringing in the ear (Tinnitus): For unknown reasons, 33% of patients with a TMJ disorder experience noise or ringing (tinnitus). Of those patients, half will have resolution of their tinnitus after successful treatment of their TMJ.
Range of Possible Treatment
When symptoms of TMJ trouble appear, an oral and maxillofacial surgeon should be consulted. A specialist in the areas of the mouth, teeth and jaws, the oral and maxillofacial surgeon is in a good position to correctly diagnose the problem.
Special imaging studies of the joints may be ordered and appropriate referral to other dental or medical specialists or a physical therapist may be made.
TMJ treatment may range from conservative dental and medical care to complex surgery. Depending on the diagnosis, treatment may include short-term non-steroidal anti-inflammatory drugs for pain and muscle relaxation, bite plate or splint therapy, and even stress management counseling.
Generally, if non-surgical treatment is unsuccessful or if there is clear joint damage, surgery may be indicated. Surgery can involve either arthroscopy (the method identical to the orthopaedic procedures used to inspect and treat larger joints such as the knee) or repair of damaged tissue by a direct surgical approach.
Once TMJ disorders are correctly diagnosed, appropriate treatment can be provided.