Definition

Temporomandibular joint dysfunction (TMJD) occurs when there is some type of pain or decreased functionality of the jaw, either due to pathology within the joint itself (intra-articular) or due to the surrounding musculature (extra-articular). It is important to note the distinction in nomenclature between the joint itself, the temporomandibular joint (TMJ), and the dysfunction of the joint that is the clinical syndrome, TMJD.

The TMJ is a synovial articulation that occurs bilaterally between the temporal bone (upper portion) and the mandible (lower portion). An intra-articular avascular fibrous disc separates the joint into an upper and lower space. This disc is attached to the lateral pterygoids anteriorly. The disc continues as retrodiscal tissue posteriorly, which is highly innervated and vascularized, and attaches to the lower condyle lamina and temporal lamina. This entire joint space is enclosed within a temporomandibular ligament ( Fig. 114.1 ).

Anatomy of the temporomandibular joint.

Image from http://www.usa.gov.

The jaw has two basic movements: a rotary or hinge-like component, which is the predominant motion of the first-third of jaw opening, and a translational component in which the mandible moves in an anteroposterior and mediolateral direction. Normal jaw opening is said to be anywhere from 40 to 50 mm. This is achieved by the synchronized relaxation and activation of the surrounding muscles of mastication during which the articular disc that separates the joint space glides anteriorly to aid the motion (translation of the jaw).

Internal derangement of the TMJ, which is a type of intra-articular manifestation, is when the disc-condyle relationship is disrupted and can be present with or without reduction. Reduction is the process of the mandibular condyle sliding over the displaced disc and eventually back into place in the mandibular fossa. The most common of these derangements is anterior displacement of the disc with or without reduction. This is very painful since the retrodiscal component, which is highly vascularized and innervated, is in contact with the articular space. A clicking noise may be heard as the mandibular condyle slides back and forth over the TMJ disc. With disease progression, reduction no longer occurs and the condyle is unable to glide over the anteriorly displaced disc. As a result, the end range of motion of jaw opening is decreased to only 25 mm. Although the exact etiology of TMJD is unknown, it is thought to be multifactorial in nature with biomechanical, neurologic, and psychosocial components contributing to the pathology. Controversial causes of TMJD include dental malocclusion (a change in bite pattern) and bruxism (repetitive jaw-muscle activity characterized by clenching and grinding the teeth together). Several studies have shown that there is limited evidence to suggest that there is an albeit weak relationship between bruxism and the development of TMJD. In regard to dental malocclusion, it remains plausible that changes in bite pattern could result in unopposed mechanical forces that put a strain on the TMJ and surrounding musculature, leading to imbalances that result in pain and remodeling of the joint space; however, there is not any evidence to support this hypothesis.

TMJD is a broad encompassing disease affecting up to 15% of the population with its peak incidence between ages 20 and 40. The disease is also twice as common in women than in men. This difference is not entirely understood; however, some studies have shown that there is a hormonal influence and elevated levels of estrogen may be a factor.

Symptoms

Symptoms of TMJD include pain within the joint space and/or related musculature (myofascial pain); increased clicking noise with mandible range of motion; and decreased range of motion/function of mandible. Pain is often the defining feature of this disease and can usually be exacerbated with palpation of the TMJ or the surrounding musculature. Patients may also present with having their jaw “lock” (abrupt decrease in jaw opening), commonly referred to as trismus, upon trying to open the jaw wider in addition to a clicking noise with jaw motion. Headaches are occasionally associated, which are often occipital in location but classified as tension or migraine in quality. Other symptoms of TMJD can include tinnitus, dizziness, and dysphagia.

Physical Examination

A physical exam should start with inspection to assess for any gross abnormalities in size near the joint space, skin integrity, and should always be compared to the opposite side of the body. Next, the joint line and muscles of mastication should be carefully palpated to evaluate for any tender or painful areas or masses. Range of motion, including end-range, and any deviation of the jaw upon opening should also be assessed. When the patient is suffering anterior displacement with reduction, there is a clicking noise that is appreciated upon opening and closing the jaw. As the pathology worsens, movement of the intra-articular disc will not be as free and, as a result, reduction will not occur ( Fig. 114.2 ). This will result in the jaw being locked upon maximal opening. It is also important to assess for any crepitus with opening, as there may be a sign of arthritic change. If there is any question of head or neck trauma, a thorough head and cervical examination should be completed as well.

Magnetic resonance image showing anterior displacement of the articular meniscus in relation to the mandibular condyle in closed-mouth position.

Reprinted with permission from Maizlin ZV, Nutiu N, Dent PB, Vos PM, Fenton DM, Kirby JM, et al. Displacement of the temporomandibular joint disk: correlation between clinical findings and MRI characteristics. J Can Dent Assoc. 2010;76:a3 <http://www.jcda.ca/article/a3> .

Functional Limitations

Based on the natural progression of internal derangement (most likely anterior disc displacement), functional limitations may take several years to decades to develop. Once pain is present, decreased range of motion of the jaw (trismus) can be seen. Pain with mastication and/or speaking may be seen. If headaches are a component of the syndrome, sleep may be affected. Because of the chronic nature of pain seen in this condition, there may be other psychosocial components that affect sleep and mood.