The temporomandibular joint (TMJ) is formed by the articulation of the mobile condyle of the mandible with the glenoid fossa of the temporal bone. The mandibular condyle and glenoid fossa are separated by a cartilaginous disc that is aneural and avascular, except at its periphery in the non-load-bearing areas. The disc aids in cushioning and dissipating joint loads, promotes joint stability when chewing, lubricates and nourishes the joint surfaces, and enables joint movements.

Medial and lateral ligaments secure the disc to the condyle. Anteriorly the disc is attached to the capsule and the superior fibres of the lateral pterygoid muscle. Posterior to the disc is the retrodiscal area that contains synovial membrane, blood vessels, nerves, loose connective tissue, fat, and ligaments. The retrodiscal ligaments help to maintain the condyle–disc relationship. The retrodiscal tissues are susceptible to high or repetitive loads such as may occur in prolonged dental work. This loading can cause inflammation of the retrodiscal tissues.

The TMJ is a source of head and facial pain; evidence suggests that the majority of patients improve with non-interventional treatment (Toller 1973; Sato 1998, 1999). The term temporomandibular disorder (TMD) is used to describe a variety of medical and dental conditions relating to TMJ dysfunction (TMJD), such as true pathology of the TMJ and involvement of the muscles of mastication.

Four categories of TMD are recognized:

There is considerable overlap in the clinical presentation of head, neck, and TMJ disorders, and many patients present with more than one condition contributing to their problem. It is essential that a detailed history is taken, and in addition to examining the TMJ, a thorough evaluation of the head, neck, and upper thoracic spine must be included in the assessment of TMJD.

Although pain is the commonest symptom of TMJD there are a variety of associated symptoms:

These symptoms may occur in isolation or any combination. When taking the history it is essential to identify factors that could be contributing to the problem and the following points should be considered:

Emotional factors can contribute to head and facial pain; high stress levels have been associated with actions such as bruxism, clenching, and chewing gum that increase the loading and forces acting on the TMJ, and can also lead to muscle overuse, fatigue, and spasm. It is important to establish whether events at work or home are causing stress, and whether patients can identify a link between this and their symptoms.

The routine examination of the TMJ includes assessment of general posture, head and neck position, the influences of the thoracic curvature, and scapulae positions. The postural position of the mandible (PPM) is observed. This is the relaxed position of the jaw, and optimal PPM is achieved when the teeth are slightly apart and the lips together; the average space between the upper and lower teeth in the PPM is 3 mm (Beyron 1954). The tip of the tongue should be resting on the roof of the palate, just behind the central incisors, with no pressure of the tongue against the teeth. The lips should be closed and the individual should be able to breathe comfortably through their nose.

An assessment of the bony and soft tissue contours of the face is made. Symmetry of the face is examined by observing the bipupital, otic, and occlusal lines, which should all be parallel. Routine examination for malocclusion should be done and the following observed:

Physiological movements of the cervical and thoracic spine should be tested, and any movement abnormalities and pain provocation noted. A full range of TMJ movements should be observed. The therapist observes the quality of movement, the range available, whether it is different from the patient’s normal range, and deviations from symmetrical trajectories. It is useful to palpate the lateral condyle either laterally or posteriorly to feel the quality of movement. During mouth opening, a small indentation can be felt posterior to the lateral pole; in cases of hypermobility, a large indentation can be felt. If there is unilateral hypermobility, the mandible deviates towards the contralateral side of the hypomobile joint.

The ranges of movement assessed are depression, elevation, protraction, retraction, and left and right lateral movement. If the movement is limited or painful, the mandible can be gently moved passively to assess the true range of movement, and any locking or rigidity felt at the end of range can assist in clinical diagnosis. If extreme muscle spasm is present, there is a rigid end-feel, whereas opening limited by disc displacement without reduction does not have such a firm end-feel (Kraus 1994).

Joint sounds during active movements can be assessed using stethoscopic auscultation. Clicking, popping, grating, grinding, and clunking are often used to describe sounds accompanying TMJ movements. Other factors that should be taken into account are:

Joint noises are often a sign of disc displacement, but they can also be caused by joint surface irregularities of soft tissue perforation or joint fluid abnormalities (Takahashi 1992).

Accurate diagnosis of TMJD may require additional investigations, such as radiographs, three-dimensional computed tomography (CT) to assess for bony abnormalities, or magnetic resonance imaging (MRI) to assess the disc and the retrodiscal tissues. Disc position during physiological movements can be viewed using cine MRI.

Myofascial pain is a component of most types of TMJD. The major muscles of mastication are the masseter, temporalis, medial, and lateral pterygoid muscles; digastric muscle is an accessory muscle of mastication. The temporalis and masseter muscles can be observed for hypertrophy and atrophy, and should be palpated for muscle texture, tenderness, and myofascial trigger points (MTrPts). The medial and lateral pterygoid muscles are difficult to palpate, and therefore, assessment is carried out using intra-oral palpation (see Fig. 2.1). Tenderness in the facial muscles is a common finding in head and neck musculoskeletal disorders, and it is useful to palpate the muscle of mastication at rest, during muscle contraction, and when on a stretch. It is also important to assess the strength and control of the deep neck flexors and scapula stabilizers. The position of the cervical and thoracic spine affects the PPM, and cervical position has an immediate and lasting influence on mandibular position (Dombrady 1966).

Figure 2.1 Intra oral palpation.

Soft tissue dysfunction is treated with myofascial techniques, manual or acupuncture trigger point deactivation, muscle relaxation, and muscle re-education, where normal movement patterns are taught. Exercises to decrease masticatory muscle activity and, hence, TMJ loading are taught (see below). These exercises also help to counteract habitual jaw bracing.

The patient places the tongue in the resting position with the tip of the tongue on the roof of the palate, just behind the top teeth. The patient is instructed to keep the teeth lightly apart and gently move the jaw from side to side. Joint noises should not be heard and the tongue must remain relaxed during the jaw movements. The therapist should ensure that the patient moves the jaw and does not get just lip movement.

The patient places the tongue in the rest position, and opens and closes the mouth while holding the tongue in a relaxed position. The movement is initially performed slowly and then at speed. It is essential that the patient does not allow the back teeth to clench together during the exercise. It is suggested that this movement has a pumping effect on the joint (McCarthy et al 1992), in which intra-articular pressure is alternately increased and decreased, influencing the movement of fluid and dissolved particles in the interstitial tissues. This exercise also helps to control opening of the mouth and prevents overloading of the TMJ.

The patient should also be given exercises aimed at improving postural control including exercises for the deep neck flexors, scapular stabilizers, and thoracic extensors.

Dental appliances such as occlusal splints and night guards are commonly used to control pain arising from clenching or bruxism. These appliances may be worn during the day, but are generally worn at night, and can take several months to fully relieve the symptoms.

Joint stiffness is a common feature of TMJD, and can be caused by capsular tightness, muscle spasm, or internal derangement of the disc. Internal derangement is the most common arthropathy and is characterized by progressive anterior disc displacement. On clinical examination joint noises are often heard. Stiffness can be treated with intra-oral passive accessory manual mobilizations aimed at improving the gliding component of jaw motion. Joint mobilizations will not permanently relocate a displaced disc. In the first 10 to 15 mm of mandibular opening, the mandibular condyle rotates beneath the disc. Forward translation of the mandible starts to occur between 10 and 15 mm of mandibular opening, in conjunction with rotation; translation occurs in the upper joint space between the disc and the maxillary fossa. If translation is restricted, mouth opening may be limited to 20 to 25 mm.

When TMJD is unilateral several common joint restrictions can be observed:

Passive intra-oral joint mobilizations can be applied to the joint to increase range of movement, particularly the forward translation. These techniques are best applied with the patient in relaxed supine lying.

This technique creates a distraction at the TMJ. The therapist stands on the opposite side of the involved joint, and using a gloved hand, places the thumb on top of the patient’s molars on the affected side. The therapist’s fingers are in a relaxed position on the patient’s chin. The therapist’s other hand stabilizes the patient’s head. A gentle force is applied parallel to the longitudinal axis of the mandible; this can be a single, sustained distraction force or oscillatory movement. The mobilization can be performed as a purely passive movement, or in combination with the patient actively opening and closing his or her mouth.

The therapist uses the same hand placement as employed in the previous technique, but the force is applied so that the condyle moves in an anterior direction. This technique can also be performed as a sustained stretch, oscillatory movement and with active movement.

The therapist stands on the opposite side to the joint involved, and using a gloved hand, places the thumb on the inside of the opposite molars; the other fingers are in a relaxed position over the jaw. The direction of force is lateral, towards the plinth and the patient’s feet. Using a multidirectional force helps to avoid joint discomfort on the contralateral side that may occur if a purely lateral force is used (Kraus 1994).

Mobilizing joint exercises are given to help maintain the increased range of joint motion. The physiological effects of intra-oral techniques are not understood. Nitzan and Dolwick (1991) suggested that an increase in translation occurs as a result of a release of the adherence of the disc to the fossa caused by a reversible effect, such as a vacuum or viscous synovial fluid.