Definition

The temporomandibular joint (TMJ) is the synovial articulation between the mandible and the cranium. The TMJ is unusual in that the articular surfaces are covered by fibrous tissue rather than hyaline cartilage, as in most joints, and that it is divided into two joint spaces by an intra-articular disc. TMJ dysfunction (TMD) includes a collection of symptoms that refer to intrinsic and extrinsic TMJ conditions. These conditions are commonly referred to as TMJ, although they should more accurately be referred to as TMD to specify a difference between the joint itself and a true dysfunction. These symptoms include issues that cause pain or dysfunction relating to the TMJ itself as well as to the muscles of mastication. Because of the high number of issues that can be manifested in the facial and temporal area, a thorough history and physical examination are necessary to identify the true cause of pain in this area.

Studies report that approximately 28% of the population exhibits signs of TMD. Of those people suffering from symptoms, 14% had actual restricted range of motion of the mandible [1]. There is historically a predominance in women (5:1 versus men), and it occurs most often in patients between the ages of 15 and 45 years [2–4]. The most common cause of TMD is myofascial pain dysfunction of the muscles of mastication, and stress is often associated with this dysfunction [5–7]. This dysfunction can also be associated with macrotrauma, such as a motor vehicle accident, or microtrauma, such as teeth grinding and clenching at night. Identification of specific mechanical causes is important as well to correct issues that may be lending themselves to TMD. Examples of mechanical causes can be prolonged mouth or upper respiratory breathing, postural abnormalities, and sleeping prone with increased pressure on the TMJ. A third major cause of TMD is dental malalignment. No matter the physical cause, stress and psychosocial impact should always be considerations [5–7].

Within the TMJ, there is a biconcave cartilage disc that normally moves with the mandibular condyle in the fossa (Fig. 113.1). The TMJ is a modified hinge joint that has two separate periods and types of motion. In the initial third of opening, the joint moves in a rotational manner. In the latter two thirds of opening, the joint moves in both a rotational and translational motion, allowing increased range of motion. Muscles commonly involved with TMD are the temporalis, masseter, and internal and external pterygoids. The TMJ is innervated by branches of the mandibular nerve. Irritation to these nerves, muscle spasms, intra-articular disease, and myofascial irritation can cause symptoms related to TMD [8].

Symptoms

Symptoms of TMD are varied and may at first seem unrelated. A common complaint with which patients may present is noise stemming from the TMJ, including crepitus, clicking, grinding, and popping. Pain at the level of the TMJ or surrounding areas also is a common complaint that may lead a patient to seek care from a health care provider. Whereas pain directly over the TMJ or mandible may lead patients to believe that they have a problem with the jaw, TMD can often be manifested as nontraditional headaches or upper cervical pain as well and is often made worse with chewing. Another common complaint in TMD is decreased range of motion of the jaw with “locking” of the joint in severe cases. Other symptoms, such as generalized facial pain, earaches, tinnitus, dysphagia, and even photosensitivity, have been reported with TMD [7,9].

Physical Examination

The diagnosis of TMD is made by observation of the range of motion of the mandible and palpation of the musculoskeletal structures of the face and head. It is essential to determine whether the patient has an intrinsic or extrinsic dysfunction of the TMJ. The translation can be felt by placing a finger over the TMJ just anterior to the tragus of the ear and asking the patient to open the mouth wide and repeat this motion. With palpation, the provider should identify whether the movement is smooth or if crepitus or joint dysfunction is noted. At maximal mouth opening, measure the opening in millimeters between the upper and lower incisal edges; the normal range is between 38 and 45 mm [10,11]. The average individual should have roughly three fingerbreadths between the teeth without any discomfort or pain. Monitoring of mandible opening for lateralization during opening can also suggest pathologic change. Have the patient also move the mandible left and right, noting restriction on one side versus the other or pain with this motion.

If the disc in the TMJ is displaced (Fig. 113.2) or if there are arthritic changes, clicking and crepitus can be heard or palpated as the disc clicks into its normal position with jaw opening. There will also be a click as the disc slips out of its normal position on closing. If the disc is fully displaced (anterior disc displacement with no reduction), there is no clicking and limited opening with an opening shift toward the locked side and no lateral movement toward the contralateral side. Full lateral and protrusive movements with limited openings might suggest muscle spasm versus disc displacement.