Temporomandibular joint disorder -- known as TMJ -- is a tongue twister that affects the jaws of more than 10 million people in the United States, mostly women. Its most common symptoms include a clicking or popping sound every time you open or close the mouth, facial tenderness, or the feeling of your jaw momentarily "being stuck." This discomfort stems from the temporomandibular joint located in front of each earlobe, which connects the lower jaw bone to the skull.

No one's really certain what causes TMJ but one thing is for sure -- it's exacerbated by stress. Many cases of TMJ go undiagnosed, because symptoms such as headaches, earaches, dizziness, ringing in the ears, neck pain, and tenderness of the jaw muscles can be confused with other conditions. "Dentists and physicians do not study TM disorders, so only the most astute clinicians will pick it up," says Michael Gelb, a clinical professor at the New York University College of Dentistry.

If facial discomfort and jaw pain persist for more than a month, visit a specialist who regularly treats TMJ. He or she may suggest a night guard designed to keep your jaw in a relaxed position inhibiting clenching and grinding, as well as other therapies. Find a specialist through the referral services at the American Academy of Orofacial Pain, aaop.org.