The temporomandibular joint (TMJ) is the hinge joint that connects the lower jaw (mandible) to the temporal bone of the skull, which is immediately in front of the ear on each side of your head. The joints are flexible, allowing the jaw to move smoothly up and down and side to side and enabling you to talk, chew, and yawn. Muscles attached to and surrounding the jaw joint control the position and movement of the jaw.

The cause of TMD is not clear, but dentists believe that symptoms arise from problems with the muscles of the jaw or with the parts of the joint itself.

Injury to the jaw, temporomandibular joint, or muscles of the head and neck — such as from a heavy blow or whiplash can cause TMD. Other possible causes include:
Grinding or clenching the teeth, which puts a lot of pressure on the TMJ
Dislocation of the soft cushion or disc between the ball and socket
Presence of osteoarthritis or rheumatoid arthritis in the TMJ
Stress, which can cause a person to tighten facial and jaw muscles or clench the teeth

Common symptoms of TMD include:
Pain or tenderness in the face, jaw joint area, neck and shoulders, and in or around the ear when you chew, speak, or open your mouth wide
Limited ability to open the mouth very wide
Jaws that get “stuck” or “lock” in the open- or closed-mouth position
Clicking, popping, or grating sounds in the jaw joint when opening or closing the mouth (which may or may not be accompanied by pain) or chewing
A tired feeling in the face
Difficulty chewing or a sudden uncomfortable bite — as if the upper and lower teeth are not fitting together properly
Swelling on the side of the face
May occur on one or both sides of the face

When the basic treatments listed above prove unsuccessful, your dentist may suggest one or more of the following treatments for TMD:
Transcutaneous electrical nerve stimulation (TENS). This therapy uses low-level electrical currents to provide pain relief by relaxing the jaw joint and facial muscles. This treatment can be done at the dentist’s office or at home.
Ultrasound. Ultrasound treatment is deep heat that is applied to the TMJ to relieve soreness or improve mobility.
Trigger-point injections. Pain medication or anesthesia is injected into tender facial muscles called “trigger points” to relieve pain.
Radio wave therapy. Radio waves create a low level electrical stimulation to the joint, which increases blood flow and relieves pain.