THE TEMPOROMANDIBULAR JOINT (TMJ) IS ONE of the most used joints in the body and, therefore, susceptible to injury. Temporomandibular disorder (TMD) is the broad term used to describe many different diagnoses that cause TMJ pain and potentially limit mouth opening. TMD can be subdivided into three physical diagnostic categories: muscle disorders, disc displacements, or joint disorders. The physical therapy examination must consist of a thorough patient history, systems screen, pain and postural assessment, palpation of joint structures and related muscles, AROM and PROM testing, resisted isometrics, functional and dynamic loading tests, as well as a cervical spine screen. The specific examination findings will assist the physical therapist in identifying the physical therapy diagnosis and the patient’s body structure and function impairments, activity limitations, and participation restrictions as part of the International Classification of Functioning, Disability and Health (ICF) classification system. A comprehensive examination and assessment will help identify the most appropriate physical therapy management for the patient and will determine the need for referral to other health care providers.

The physical therapy management of a patient with TMD must consider all of the contributing factors that are causing the patient’s symptoms, including their parafunctional habits, posture, and psychosocial characteristics to name a few. Many research studies on specific research interventions for TMJ do not have rigorous methodology and, therefore, their recommendations for the best interventions must be considered cautiously. Research has shown some cautiously positive improvement in symptoms for patients with TMD when the physical therapist utilizes active exercises, manual therapy, postural re-education, relaxation techniques, biofeedback, or mid-laser therapy, as well as combinations of these treatment interventions.

The temporomandibular joint (TMJ) opens and closes approximately 2,000 times per day as it accommodates a full day worth of chewing, talking, swallowing, yawning, and snoring. This makes the TMJ the most active joint in the body and susceptible to injury.¹ Temporomandibular disorder (TMD) is the term used to describe pathology associated with pain in the jaw, muscles of mastication, and other related structures.² There is a close association between alignment of the cervical spine, jaw, and teeth. Any dysfunction, or aberrant movement patterns, of one or more of these components may, therefore, lead to TMD. There are many potential causes of TMD, and its etiology is often multifactorial. Posture, jaw, or dental malocclusion, and parafunctional habitual activities, including bruxism and chewing gum, may all play a role in the development of TMD. Additionally, inflammatory or degenerative conditions, trauma, and stress also contribute to its development. Psychological stress is not only a potential cause for TMD, but it may prolong and amplify its symptoms in individuals.³

Upwards of 50% to 75% of the population may present with at least one symptom of TMD within their lifetime; however, only a small percentage of those individuals seek medical treatment.^4,5 Although TMD can affect people of all ages, studies have found that TMD is more prevalent in women than men, and women between the ages 20 to 40 are most likely to seek treatment.^6,7 Approximately 8% to 15% of women may develop chronic symptoms according to a study by Dao and LeResche.⁸ The average age of a patient with TMD was 35.6 years, and the majority of patients ranged in age from 26 to 40.⁹ Studies have also suggested a four to one gender bias in favor of females, which is consistent with previous research.⁹

Anatomy

The TMJ is a biconcave, synovial, hinge joint that allows for mandibular depression (mouth opening and closing), protrusion, retrusion, and lateral deviation of the jaw (Table 92–1). There is an intraarticular disc that articulates with the mandibular fossa of the temporal bone superiorly and the condyle of the mandible inferiorly. The presence of the disc divides the joint into two compartments which perform separate accessory movements that are essential for the full range of motion and function of the jaw. Gliding and sliding (translation) occur in the superior compartment, and rotation occurs in the inferior compartment (Fig. 92–1).¹⁰ The muscles of mastication include the masseter, temporalis, lateral pterygoid, medial pterygoid, and suprahyoids (Table 92–2). Since the TMJ and most of the muscles of mastication are innervated by the mandibular branch of the trigeminal nerve (CN V), pain associated with TMD may be localized to the TMJ or referred to the face in the distribution of the trigeminal nerve. The exception to this innervation pattern is the surprahyoid which is innervated by CN V, VII, XII (Fig. 92–2).¹⁰

Mouth opening is initiated when the superior head of the lateral pterygoid pulls the disc anteriorly, allowing for rotation of the mandibular condyle. This rotation, occurring during the first 25 mm of mouth opening, occurs in the inferior joint compartment. Full mouth opening is achieved when translation of the condyle and disc on the articular eminence occurs in the superior joint compartment. Motion is checked by the joint capsule and surrounding ligaments. The resting position of the jaw is the position with the mouth slightly open, lips together, teeth slightly separated, and the tongue resting on the hard palate.¹⁰ The teeth are clenched in the closed packed position. The capsular pattern of the TMJ is limitation of mouth opening (Table 92–3). Normal ROM (range of motion) for mouth opening is 40 mm and occurs as described above with both rotation and translation. Normal ROM for jaw protrusion and retrusion is 3 to 6 mm and occurs primarily with translation of the mandibular condyle. Lateral excursion, normally 10 to 15 mm, occurs with ipsilateral rotation and contralateral translation of the mandibular condyles. During lateral excursion, the ipsilateral condyle (condyle on the side to which the mandible is moving) remains relatively stationary and rotates and the contralateral condyle translates anteriorly and inferiorly and toward the motion side. Table 92–1 summarizes the normal ROM of TMJ.¹⁰

Pathophysiology

Pathology may be associated with the muscles of mastication, joint structures, or inflammatory conditions and can all cause TMD. Muscle disorders and repetitive stress may occur from overuse of the muscles during parafunctional behaviors, prolonged strain associated with forward head posture, and fibromyalgia. Overuse or overstretching of the mastication muscles may also occur during prolonged mouth opening during dental procedures or as a result of trauma. Trigger points, or palpable nodules, may develop in the muscles of mastication or in local cervical muscles causing referred pain to the TMJ.¹¹ Trigger points located in the upper trapezius, sternocleidomastoid, and other cervical muscles typically have referral patterns to the ipsilateral TMJ.¹¹ Overactive muscles of mastication not only cause pain, they can also cause faulty biomechanics and influence disc displacement pathology described below (Figs. 92–3, 92–4, and 92–5 UT/SCM pain referral patterns).

Internal derangement is the former term used to describe pathology involving the joint structures in the TMJ including disc displacement. Classification of disc displacements can be subdivided into three groups with differing pathomechanics that include disc displacement with reduction (DDWR); disc displacement without reduction (DDWOR) and limited mouth opening; and disc displacement without reduction and without limited mouth opening (Figs. 92–6, 92–7, and 92–8).¹² Disc displacement with reduction occurs when, during mouth opening, the disc moves too far anteriorly, possibly due to an overactive lateral pterygoid or stretched posterior capsule and ligaments of the TMJ, and the condyle of the mandible moves past the posterior edge of the disc, creating a click (Fig. 92–6). The jaw usually deviates toward the side of the click. The disc returns to its normal position after the condyle stops moving. A softer, reciprocal click may also be heard with mouth closing, usually as a result of overactivation of the lateral pterygoid muscle (Fig. 92–7).¹⁰

Disc displacement without reduction (DDWOR) occurs when the disc does not reduce and remains anterior to the mandibular condyle. This may be associated with limited opening, or closed locking, of the jaw if the disc blocks further opening movements (Fig. 92–8). Generally, the condylar rotation occurs to allow 25 to 30 mm of mouth opening but translation is blocked by the anteriorly displaced disc, causing a limitation in full mouth opening. The jaw deviates to the side of the pathology and lateral excursion may be reduced to the contralateral side of the pathology.¹⁰ DDWOR without limitation of mouth opening occurs when the disc is fully displaced anteriorly.

Patient History

Similar to the examination of other joints, a thorough patient history will assist in guiding the TMJ examination. The physical therapist should ask questions regarding patient’s medical history, the onset and course of symptoms including the history of trauma, previous surgeries, dental procedures, and prior history of cervical spine disorders. Gaining knowledge of the patient’s daily activities will give the physical therapist insight into repetitive trauma and static postures that may affect the TMJ mechanics. This will not only help the physical therapist determine the etiology of the symptoms but guide the intervention and patient education plan as well. The patient’s daily habits, household tasks, work practices, computer use, sitting posture, desk setup, sleep habits, diet, parafunctional behaviors (including bruxism, gum chewing, clenching teeth, nail and lip biting, and resting the chin on the hands), all influence the mechanics of the TMJ. Any of these factors may lead to or prolong symptoms of TMD. There has been strong links found between psychological stress and presence of TMD.³ Asking the patient about the presence of emotional or psychological stress is imperative to obtain a complete understanding of the patient’s background and determining the potential causes of TMD. This will assist the physical therapist with the potential need for referral to additional health care providers.

Several self-report questionnaires exist for the evaluation of TMD including the Disability Index Questionnaire, Jaw Functional Limitation Scale (JFS), and the Neck Disability Index (NDI). Olivo et al, in a 2010 study looking at the association between Neck and Jaw disability, found a strong relationship between the two disorders.¹³ Proceeding with a physical therapy examination of both the cervical spine and jaw must be considered to complete a thorough evaluation of the patient.

Signs and Symptoms

Symptoms of TMD include unilateral or bilateral jaw pain, joint noises (including popping, crepitus, and clicking), headache and/or cervical pain, dizziness, earache, and tinnitus.

Clinical signs of TMD include limited mouth opening <40 mm and the reproduction of joint or muscle pain and joint sounds.

Systems Review

The systems review will include screening for headache, cervical spine disorders, neurological, and other pathologies that will help rule out differential diagnoses that require referral to other health care providers for additional medical workup. Headaches can be classified as primary headaches, which include cluster, migraine, and tension type headaches, or cervicogenic headaches. Jull et al in 2007 described three objective measures: reduced cervical spine ROM, pain with upper cervical segmental mobility testing, and weakness in the deep cervical flexor muscle groups, that when found in combination had 100% sensitivity and 90% specificity in determining cervicogenic headache versus primary headache.¹⁴ Patients who present with migraine and tension headaches should be referred to other providers to address those conditions, which may occur in conjunction with ongoing physical therapy intervention. Soft tissue assessment of cervical musculature, including but not limited to the upper trapezius and sternocleidomastoid muscles, will rule out these common trigger point referral patterns to the TMJ (see Figs. 92–2 and 92–3).¹¹ Screening the oral-facial structures including the teeth, eyes, ears, and sinus as potential referral sources for jaw pain should be considered and referred to specialists as needed. Screening the cardiovascular system with vital sign assessment, at a minimum, is necessary since jaw pain is an anginal equivalent, especially in females. Any jaw pain that is present during or after cardiovascular exertion must not be ignored and referral to the proper medical doctor is warranted. Psychological and neurological causes for jaw pain must also be considered and result in referrals to the proper specialists.