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What is the TMJ?

TMJ is the abbreviation for temporomandibular joint. Everyone has two of these joints, and the term “TMJ” refers to the normal, healthy joint on each side of the skull that allows the lower jaw to function during speech, swallowing, and chewing. The name of the joint comes from the two bones that make up each side of the joint. Like all joints, the TMJ is made of muscle, ligaments, cartilage, and bone with supporting nerves and nutritional supply in the form of synovial fluid.

The temporal bones of the skull form the “roof” and “inside” of the TMJ, and the mandible (lower jaw) makes up the floor of the joint, which moves in three directions: It rotates around an imaginary axis for the first part of the opening stroke of the jaw and the last part of the closing stroke; it translates , or slides, down and forward from the endpoint of rotation to maximum jaw opening; and, it moves side to side. Specifically, the part of the mandible that is involved with the TMJ is called the condyle, and the part of the temporal bone involved in the joint is called the temporal fossa. Because the TMJ moves in three planes of space, unlike all other joints in the body that move like a hinge, the TMJ is called a ginglymoarthroidal joint. Between the two bones is a cartilaginous disc that serves as sort of a shock absorber to protect the joint that slides with the condyle during the range of motion. Attaching to the disc and the mandible is a specific muscle, called the lateral pterygoid that pulls the disc and the jaw forward as the jaw translates. There also ligaments that hold the disc to the condyle on each side of the disc, called collateral ligaments.


This model represents a healthy TMJ showing the disc (blue) properly positioned between the condyle and temporal fossa. The muscles shown are the main jaw closing muscles.

A discussion of the TMJ is not complete without mentioning that the mandible is essentially a bone floating in space. In fact, when ancient skulls are discovered in archaeology, the mandibles are usually absent because the soft tissue has all been lost, allowing separation of the mandible from the skull.

This means that the function, health, and stability of the TMJ is totally dependent on the supporting muscles and ligaments of the head and neck and the teeth that provide a stop at the right place for optimal chewing strength.

The masseter muscles, the temporalis muscles, the digastric muscles, the medial pterygoid muscles, and the lateral pterygoid muscles are the primary muscles involved in jaw function. Since these muscles all work by pulling on the bones of the skull, it is important to consider that the skull is like a bowling ball balancing on a broken broomstick, which is the spine. This balancing act requires harmony in function of many supporting muscles of the upper back, neck, chest, and shoulders. Therefore, it is easy to understand how many problems of the head, neck, and upper back can manifest themselves as TMJ problems; sometimes, TMJ problems can also present as dental problems, neck pain, headaches, etc. Often, the term “TMJ” is incorrectly used to refer to a problem that does not easily fit another diagnosis by the medical community.

VIDEO: TMJ Disorder


What is TMD?

When any part of the anatomical structures or supporting structures of the TMJ is injured or damaged, dysfunction occurs. While “TMJ” refers to the temporomandibular joint itself, “TMD” refers to temporomandibular disorder. TMD syndrome is a vague term that usually involves one or more conditions listed below and/or others not mentioned:

  • TMD

    This model represents and injured TMJ where the disc (blue) is displaced and the condyle is degenerating.


  • Tendonitis
  • Myofascial pain
  • Myositis
  • Myalgia
  • Osteoarthritis
  • Degenerative Joint Disease
  • Retrodiscitis
  • Tinnitis
  • Headaches of various types
  • Dislocation of the disc
  • Subluxation of the disc
  • Muscle spasm
  • Cervicalgia

TMD Treatment

Treatment for TMD is dependent on the specific diagnoses involved and is typically directed to resolving pain rather than reducing joint noises (popping, clicking, etc.). Joint noises are evidence that injury has occurred and are signs rather than symptoms. Pain, compromised quality of life, and compromised function, however, are symptoms that treatment is typically directed toward.

Treatment for TMJ disorders is controversial, and clinicians often differ in their approach. Some tend to treat physically (physical therapy, bite splint therapy, chiropractic, etc.), some tend to approach treatment from a medical model (medications, mental health therapy, etc.), and some practice the philosophy that TMD tends to be self-limiting and opt not to treat but rather provide supportive care only.

The reality is that successful management of TMD usually involves elements of each approach and often requires a team approach involving some or all of the following healthcare providers: dentist, mental health specialist, family physician, physical therapist, chiropractor, massotherapist, orofacial pain specialist, oral surgeon, etc.

Because TMD is often a chronic pain disorder, compromises in mental health in the form of depression, anxiety, psychosomatic conditions, all of which may require the assistance of a psychiatrist.

Dentists often use bite splints to treat TMD syndrome

The type of splint used should be dependent on a specific diagnosis of a specific condition. For this reason, different types of splints may be used at different times during the treatment of TMD. In fact, splints may actually also be used for diagnostic purposes to rule out complicating factors.

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