Each person has two, located on each side of the face, immediately in front of the ears, where the temporal bone of the skull connects to the lower jaw ( mandible ). TMJs open and close like a hinge, and slide forward, back, and side to side. During chewing, they experience enormous pressure.
As with other joints, the surfaces of TMJs are covered with cartilage. Like the knee, the two parts of the jaw joint are separated by a small disc, the meniscus , which prevents the bones from rubbing against each other. The muscles that open and close the mouth also help stabilize these joints, located about ½ inch (1.25 cm) in front of each of the ear canals.
TMJs and the muscles around them are prone to various disorders, which most often occur in people between the ages of 20 and 50. In the majority of cases, temporomandibular joint dysfunction is explained by muscle strains, anatomical problems and injuries. Sometimes there can also be a psychological component.
Like all joints, TMJs can be affected by osteoarthritis, rheumatoid arthritis and other inflammatory disorders. In rare cases, tumors may appear there. But, for the majority of people, pain in the TMJ region is not serious. Discomfort and pain can be temporary or chronic. They sometimes disappear without major treatment.