The temporomandibular joints (TMJs) connect your lower jaw to your skull. There are two matching joints -- one on each side of your head, located just in front of your ears. The abbreviation "TMJ" literally refers to the joint but is often used to refer to any disorders or symptoms of this region. Such problems include popping sounds in the jaw, inability to fully open the mouth, jaw pain, headaches, earaches, toothaches, and various other types of facial pain.

Many TMJ-related symptoms are caused by the effects of physical and emotional stress on the structures around the joint. These structures include the muscles of the jaw, face, and neck; the teeth; the cartilage disk at the joint; and nearby ligaments, blood vessels, and nerves.

For example, daily stress can lead you to clench and grind your teeth, both during the day and at night while you sleep. Clenching means you tightly clamp your top and bottom teeth together, especially the back teeth. The stressful force of clenching causes pressure on the muscles, tissues, and other structures around your jaw.

Many people who clench also grind their teeth. Grinding is when you slide your teeth over each other, generally in a sideways, back-and-forth movement. This action may wear down your teeth and be noisy enough at night to bother sleeping partners.

Poor posture can also be an important factor. For example, holding the head forward while looking at a computer all day strains the muscles of the face and neck.

Other factors that might aggravate TMJ symptoms are inability to relax, poor diet, and lack of sleep.

All of these stresses can result in "trigger points" -- contracted muscles and pinched nerves in your jaw, head, and neck. Trigger points can refer pain to other areas, causing a headache, earache, or toothache.

Other possible causes of TMJ-related symptoms include arthritis, fractures, dislocations, and structural problems present since birth.

• Headache
• Earache (the joint is located right in front of the ears and can easily be interpreted as ear pain; in addition, pain may be referred to the ear from nearby muscles)
• Jaw pain or tenderness of the jaw
• Dull, aching facial pain
• Biting or chewing difficulty or discomfort
• Clicking sound while chewing or opening the mouth
• Grating sensation while chewing
• Reduced ability to open or close the mouth