The temporomandibular joints are the connections between the temporal bones of the skull and the lower jawbone (mandible). There are two temporomandibular joints, one on each side of the face just in front of the ears. Ligaments, tendons, and muscles support the joints and are responsible for jaw movement.
The temporomandibular joint is one of the most complicated joints in the body: It opens and closes like a hinge and slides forward, backward, and from side to side. During chewing, it may sustain an enormous amount of pressure depending on the position and health of the upper and lower teeth, which act much like a doorstop for the joints during closing. The temporomandibular joint contains a piece of special cartilage called a disk. The disk keeps the skull and the lower jawbone from rubbing against each other.
Temporomandibular disorders, previously called TMJ (temporomandibular joint) disorders, are most common among women in their early 20s and between the ages of 40 and 50. In rare cases, infants are born with temporomandibular joint abnormalities. Temporomandibular disorders include problems with the joints, the muscles, and the bands of fibrous tissue that connect them (fascia).
Most often, the cause of a temporomandibular disorder is a combination of muscle tension and anatomic problems within the joints. Sometimes, there is a psychologic component as well. Clenching and grinding of the teeth, injury, misaligned and missing teeth, and even constant gum chewing can cause symptoms. Specific causes include muscle pain and tightness, internal temporomandibular joint derangement, arthritis, ankylosis, and hypermobility.
Muscle pain and tightness:
Muscle pain and tightness around the jaw (myofascial pain syndrome) are caused mainly by muscle overuse, often brought on by problems of misalignment of the upper and lower sets of teeth, missing teeth, injury to the head or neck, emotional stress, sleep disorders, or even toothache. Pain is also caused by trying to open the jaw too widely. Muscle pain and tightness can also result from clenching or grinding the teeth (bruxism) at night due to psychologic or sleep-related stress. Clenching and grinding while asleep exert far more force than clenching and grinding while awake. Muscle pain and tightness are more common among women and typically affect women in their early 20s and women who are nearing or going through menopause.
Internal temporomandibular joint derangement:
In the most common form of internal TMJ derangement, the disk inside the joint lies in front of (anterior to) its normal position. The disk can be moved out of place when the jaw muscles are in spasm. Spasm may occur in people born with jaw abnormalities or who have TMJ arthritis. Internal TMJ derangement can occur with or without reduction. Reduction means the parts of a joint have returned to their normal positions. Disk displacement with reduction is more common than displacement without reduction and occurs in about one third of the adult population. In derangement with reduction, the disk lies in front of its normal position only when the mouth is closed. As the mouth opens and the jaw slides forward, the disk slips back into its normal position. As the mouth closes, the disk slips forward again. In internal TMJ derangement without reduction, the disk never slips back into its normal position, and the degree to which the mouth can be opened is limited. TMJ derangement can cause inflammation around the joint (capsulitis).
Arthritis in a temporomandibular joint may result from osteoarthritis, rheumatoid arthritis, infectious arthritis, or injury, particularly injury that causes bleeding into the joint. Such injuries are fairly common among children who are struck on the side of the chin.
Osteoarthritis, a type of arthritis in which the cartilage of the joints degenerates (see Joint Disorders: Osteoarthritis (OA)), is most common among people over age 50. The cartilage in the temporomandibular joints is not as strong as the cartilage in other joints. Osteoarthritis occurs mainly when the disk is missing or has developed holes.
Rheumatoid arthritis, a disease in which the body attacks its own cells (an autoimmune disease), causing inflammation (see Joint Disorders: Rheumatoid Arthritis (RA)), affects the temporomandibular joint in about 17% of people with this type of arthritis. The temporomandibular joint generally is the last joint to be affected by rheumatoid arthritis.
Infectious arthritis is caused by an infection that has spread from an adjoining area of the head or neck or that has been carried by the bloodstream from another part of the body (see Bone and Joint Infections: Infectious Arthritis).
Traumatic arthritis, which is arthritis caused by an injury (such as when the jaw is stretched widely during a difficult tooth extraction), is rare.
Ankylosis is loss of joint movement resulting from fusion of bones within the joint or from calcification (the deposit of calcium into body tissues) of the ligaments around it. Ankylosis most often results from an injury or an infection, but it may be apparent at birth or a result of rheumatoid arthritis.
Hypermobility (looseness of the jaw) results when the ligaments that hold the joint together become stretched. In hypermobility, dislocation is usually caused by the shape of the joints, ligament looseness (laxity), and muscle tension. It may be caused by trying to open the mouth too wide or by being struck on the jaw.
Symptoms of temporomandibular disorders include headaches, tenderness of the chewing muscles, and clicking or locking of the joints. Sometimes the pain seems to occur near the joint rather than in it. Temporomandibular disorders may be the reason for recurring headaches that do not respond to usual medical treatment. Other symptoms include pain or stiffness in the neck radiating to the arms, dizziness, earaches or stuffiness in the ears, and disrupted sleep.
People with temporomandibular disorders often have difficulty opening their mouth wide. For example, most people without temporomandibular disorders can place the tips of their index, middle, and ring fingers held vertically in the space between the upper and lower front teeth without forcing. For people with temporomandibular disorders (with the exception of hypermobility), this space usually is markedly smaller.
Muscle pain and tightness:
People with muscle pain feel pain and tightness on the sides of the face upon awakening or after stressful periods during the day. Nighttime clenching and grinding of the teeth may cause a person to awaken with a headache, which may slowly diminish over the day. However, people have symptoms during the day, including a headache, if they continue to clench and grind their teeth while awake. As the jaw opens, it may move slightly (deviate) to one side or the other and may not open all the way. The chewing muscles are typically painful and tender to the touch.
Internal temporomandibular joint derangement:
Internal joint derangement related to anterior disk displacement with reduction usually causes a clicking or popping sound in the joint when the mouth opens wide or the jaw shifts from side to side. Other people are sometimes able to hear these sounds. In many people, these joint sounds are the only symptoms. However, some people experience pain, particularly when chewing hard foods. In a small percentage of people who have missing teeth and who grind their teeth, these sounds progress to locking of the joints.
Internal joint derangement related to anterior disk displacement without reduction does not cause a sound but usually causes symptoms of pain and makes it difficult for people to open their mouth wide, as is typical of most temporomandibular disorders. After 6 to 12 months, the pain may decrease, but the limited degree to which the mouth can be opened generally persists.
With osteoarthritis, because it occurs mainly when the disk is missing or has developed holes, the person feels a grating sensation in the temporomandibular joints when opening and closing the mouth, stiffness, mild pain, or a combination. When osteoarthritis is severe, the top of the jawbone flattens out, and the person cannot open the mouth wide. The jaw may also shift toward the affected side, and the person may be unable to move it back.
Rheumatoid arthritis causes pain, swelling, and limited movement. It usually affects both temporomandibular joints about equally, which is rarely the case in other types of temporomandibular disorders. When rheumatoid arthritis is severe, especially in children, the top of the jawbone may degenerate and shorten, causing deformities of the face. This damage can lead to sudden misalignment of many or all of the upper and lower teeth. If the damage is severe, the jawbone may eventually fuse to the skull (ankylosis).
In infectious arthritis, the area over and around the temporomandibular joint is inflamed, and jaw movement is limited and painful.
Traumatic arthritis causes pain, tenderness, and limitation of movement.
Typically, calcification of the ligaments around the joint (extra-articular ankylosis) is not painful, but the mouth can open only about 1 inch (about 2½ centimeters) or less. Fusion of bones within the joint (intra-articular ankylosis) causes pain and more severely limits jaw movement.
In a person with hypermobility, the jaw may slip forward completely out of its socket (dislocate), causing pain and an inability to close the mouth. Dislocation (see Urgent Dental Problems: Jaw Dislocation) may occur suddenly and repeatedly.
A dentist or doctor almost always diagnoses a temporomandibular disorder based solely on a person's medical history and on a physical examination. Part of the examination involves gently pressing on the side of the face or placing the little finger in the person's ear and gently pressing forward while the person opens and closes the jaw and listening and feeling for sounds of catching, clicking, or popping. Also, the doctor gently presses on the chewing muscles to detect pain or tenderness and notes whether the jaw slides when the person bites. Doctors ask the person to open the mouth as wide as is comfortable. An average-sized person can open the mouth at least 1½ inches (about 4 centimeters).
When a doctor suspects internal joint derangement, further tests can be done. Magnetic resonance imaging (MRI) is the standard with which doctors assess whether internal joint derangement has occurred or why a person is not responding to treatment.
A doctor suspects osteoarthritis when a creaking sound is heard when the person opens the mouth (crepitus). X-rays and a computed tomography (CT) scan can confirm the diagnosis.
Infectious arthritis may be suspected when the area over and around the temporomandibular joint is inflamed and when movement of the joint is painful and limited. Infection in another part of the body serves as a clue as well. To confirm the diagnosis of infectious arthritis, the doctor may insert a needle into the temporomandibular joint and withdraw fluid (aspiration), which is then analyzed for bacteria.
If hypermobility is the cause, the person typically can open the mouth wider than the breadth of three fingers. The jaw may be chronically dislocated. If ankylosis is the cause, the jaw's range of motion tends to be markedly reduced.
Treatment varies considerably according to the cause. Two common treatments are splint therapy (also called a mouth guard) and analgesics such as nonsteroidal anti-inflammatory drugs (NSAIDs) to relieve pain.
Muscle pain and tightness:
A splint usually is the main treatment for jaw muscle pain and tightness. For people who realize that they clench or grind their teeth, splint therapy can help them break the habit. A thin plastic splint is made by a dentist to fit over either the upper or the lower set of teeth and is adjusted to give the person an even bite. The splint, usually worn at night (a nightguard), reduces grinding, allowing the jaw muscles to rest and recover. For pain during the day, a splint allows the jaw muscles to remain relaxed and the bite to be stable, thereby reducing discomfort. The splint can also prevent damage to teeth that are under exceptional stress from the grinding. Day splints are worn only until symptoms subside, usually less than 8 weeks. Longer use may be warranted depending on the severity of symptoms.
Physical therapy may also be prescribed. Physical therapy may involve ultrasound treatment, electromyographic biofeedback (in which the person learns to relax the muscles), spray and stretch exercises (in which the jaw is stretched open after the skin over the painful area has been sprayed with a skin refrigerant or numbed with ice). Transcutaneous electrical nerve stimulation (TENS) also may help. Stress management, sometimes along with electromyographic biofeedback, and counseling help some people.
Drug therapy may also be helpful. For instance, muscle-relaxing drugs, such as cyclobenzaprine, may be prescribed to ease tightness and pain, particularly while the person waits for a splint to be made. However, these drugs are not a cure, generally are not recommended for older people, and are prescribed for only a short time, usually for a month or less. Analgesics such as aspirin or other NSAIDs also relieve pain. A prescription for opioid analgesics is usually not given because treatment may be needed for some time and these drugs can be addictive. Sleep aids (sedatives) may be used occasionally and for a short time to help people who have trouble sleeping because of the pain. Botulinum toxin injected into the muscle has recently been used successfully to relieve muscle spasms.
Regardless of the type of treatment, most people experience significant relief within about 3 months. If the symptoms are not severe, many people recover without treatment within 2 to 3 years.
Internal temporomandibular joint derangement:
In internal joint derangement with or without reduction, treatment is needed only if a person has jaw pain or trouble moving the jaw. People are given NSAIDs for pain. If a person seeks treatment right after symptoms develop, a dentist or doctor may be able to manually move the disk back into its normal position. If a person has had the disorder for fewer than 6 months, a splint may be applied to hold the lower jaw forward. This splint keeps the disk in position, permitting the supporting ligaments to tighten. Over 2 to 4 months, the splint is adjusted to allow the jaw to return back to its normal position, with the expectation that the disk will remain in place.
A person with internal joint derangement with or without reduction should avoid opening the mouth wide—for instance, when yawning or biting into a thick sandwich—because injured joints are not as protected in these activities as would be a normal jaw. People with this disorder are advised to cut food into small pieces and to eat food that is easy to chew.
Sometimes the slipped disk becomes stuck in front of the temporomandibular joint, preventing the jaw from opening fully. The disk must then be manually moved out of position to allow the joint to move fully. Passive jaw motion devices, which stretch the jaw, have been used to slowly increase jaw motion. These devices are used several times a day. One such device is a threaded screw-type instrument that is placed between the front teeth and turned, much like a car jack, to gradually create a wider opening. If such a device is not available, then a doctor may use a stack of tongue depressors placed between the front teeth, with an additional tongue depressor being added to the middle of the stack.
If internal joint derangement cannot be treated by nonsurgical means, an oral-maxillofacial surgeon may need to reshape the disk and sew it back into place. However, the need for traditional surgery is relatively rare since the introduction of procedures such as arthroscopy (see Diagnosis of Musculoskeletal Disorders: Arthroscopy). All surgical procedures are used in combination with splint therapy.
A person with osteoarthritis in a temporomandibular joint needs to rest the jaw as much as possible, use a splint or other device to control muscle tightness, and take an analgesic (such as acetaminophen or an NSAID) for pain. The pain usually goes away in 6 months with or without treatment. Even without treatment, most of the symptoms subside, probably because the band of tissue behind the disk becomes scarred and functions like the original disk. Usually, jaw movement is sufficient for normal activities, though the jaw may not open as wide as it used to.
Rheumatoid arthritis of the temporomandibular joint is treated with the drugs used for rheumatoid arthritis of any joint (see Joint Disorders: Drugs for Rheumatoid Arthritis). NSAIDs may be given for severe pain. Maintaining joint mobility and preventing fusion of the joint are particularly important. Usually, the best way to accomplish these goals is by exercising the jaw under a physical therapist's direction. To relieve symptoms, particularly muscle tightness, the person wears a splint at night. A splint that does not restrict jaw movement is used. If joint fusion freezes the jaw, the person may need surgery and, in rare cases, an artificial joint to restore jaw mobility.
Infectious arthritis is treated with antibiotics, proper hydration, pain control, and restriction of movement. Penicillin is usually the antibiotic used initially, until test results determine the type of bacteria present and thus the best antibiotic to use. Pus in the joint, if present, may be removed with a needle. Once the infection is controlled, people do jaw-opening exercises to help prevent scarring and limitation of motion.
Traumatic arthritis is treated with NSAIDs, application of heat, a soft diet, and restriction of jaw movement.
Occasionally, jaw-opening exercises help people with calcification, but people with calcification or bone fusion usually need surgery to restore jaw movement.
Prevention and treatment of dislocation resulting from hypermobility are the same as those for other causes of a dislocated jaw (see Urgent Dental Problems: Jaw Dislocation). When dislocation occurs, a helper is sometimes needed to snap the jaw back into position. Many people who experience repeated dislocations, however, learn how to maneuver the joint back into place themselves by consciously relaxing the muscles and lightly shifting the lower jaw until it pops back into place. Surgery to tighten the ligaments of the temporomandibular joint is sometimes necessary to prevent recurrent dislocations.
Last full review/revision May 2013 by Noshir R. Mehta, DMD, MDS, MS