Chapter objectives
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Describe the bony anatomy, ligamentous structures, and surrounding musculature of the temporomandibular joint, including their functions.
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Understand the arthrokinematics and biomechanics of the temporomandibular joint that occur during osteokinematic movements of the mandible.
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Recognize the relationship and causative factors of the cervical spine as it relates to pathology of the temporomandibular joint.
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Perform a thorough and systematic evaluation of the temporomandibular joint.
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Design and implement a treatment program that includes both a manual and therapeutic exercise program based on the clinical findings.
Sports rehabilitation specialists often manage athletes with complaints of head, neck, or maxillofacial pain in which the etiologic factors of their complaints can be difficult to diagnose. Disorders and complaints of pain and dysfunction can be difficult to care for because of the wide spectrum of pathology of dental, infectious, metaplastic, musculoskeletal, neurologic, otolaryngologic, psychologic, and vascular origin. The temporomandibular joint (TMJ) is a complex synovial joint with a capsule and meniscus that connects the mandible with the cranium. This joint is connected not only to the cranium but also to the spine and shoulder girdle via soft tissue attachments. Therefore, when evaluating and treating athletes with possible TMJ disorders, the clinician should assess the cranium, cervical and thoracic spine, and TMJ as one functional unit because of the interdependency and functional relationship of these joint systems. The TMJ can both refer pain and be a referral site of pain, thus complicating clinical assessment. A multidisciplinary approach is used that includes conservative rehabilitation to address joint mechanics, postural adaptations, and muscular function and control, as well as dental care and possibly the use of oral appliances.
Anatomy
Temporomandibular Joint
The TMJ is a complex synovial joint that is formed by the articulation of the mandibular fossa of the temporal bone and the condyle of the mandible ( Fig. 15-1 ). The TMJ differs from other synovial joints by the presence of teeth, which can offer anterior stabilization during surface articulation. The temporal bone forms the roof of the TMJ, the concave mandibular fossa marks the posterior border, and the convex articular eminence forms the anterior boundary. The articular surface of the mandibular fossa is composed of fibrocartilage, not hyaline cartilage, and is nonarticular because of the presence of the posterior band of the temporomandibular disk. This fibrocartilaginous surface provides greater pliability during translation and increased tensile strength for prolonged pressure and friction. The posterior border of the mandibular fossa is formed by the postglenoid spine or process. The postglenoid spine is a downward extension of the squamosal portion of the temporal bone that is located anterior to the external auditory meatus. The postglenoid spine serves as an attachment site for the capsule. The articular tubercle, which is the most anterior portion of the roof of the TMJ, is separated from the articular eminence by the articular crest. The articular eminence is convex anteroposteriorly and concave mediolaterally. With mandibular opening, the condyle translates along the eminence. However, with full mouth opening, the mandible may translate onto the articular tubercle, a condition indicative of TMJ hypermobility.
The condyle of the mandible forms the floor of the TMJ. This condyle is biconvex and has an elliptical shape measuring approximately 20 mm mediolaterally and 10 mm anteroposteriorly ( Fig. 15-2 ). This elliptical shape is oriented approximately 15° to the frontal plane, which places the lateral pole of the condyle anterior to the transverse axis of the condyle and the medial pole posterior to the frontal plane. The coronoid process is a projection located at the superior border between the neck and the ramus (of the mandible) that serves as the attachment for the temporalis muscle. Inferior to the head of the condyle is the neck, which continues as the ramus before becoming the body of the mandible. The maxillary teeth are contained in the maxillary bone. The position, form, and relationship of the teeth are important to function of the TMJ in that they can affect positioning during occlusion, with deviations or irregularities creating malocclusion. Centric occlusion or maximum intercuspation has been defined as the “relationship of the mandible to the maxilla when the teeth are in maximum occlusal contact, irrespective of the position or alignment of the condyle-disc assemblies.”
The articular disk is a firm yet flexible biconcave fibrocartilage structure consisting of dense bundles of collagenous fibers, which allows it to conform to the incongruence of the TMJ ( Fig. 15-3 ). The TMJ is divided into two compartments or spaces by the disk. The superior compartment is formed by the articulation of the superior surface of the meniscus and the glenoid fossa, whereas the inferior compartment is located between the inferior surface of the meniscus and the condylar head. The superior joint space is larger, with a volume of 1.2 mL, than the inferior compartment, which has a volume of 0.9 mL.
The articular disk can be divided into three bands based on thickness: anterior (pes meniscus), intermediate (pars gracilis), and posterior (pars posterior). The peripheral portions of the disk are non–load-bearing regions that are vascularized and innervated, whereas the intermediate band of the disk, located between the temporal bone and the head of the condyle, is avascular and aneural and is the portion of the disk where load bearing occurs. The anterior band is anterior to the condyle on the articular eminence and serves as an attachment site for the superior division of the lateral pterygoid muscle. The anterior disk attaches to the anterior joint capsule and to the superior head of the lateral pterygoid muscle. The thinnest portion of the disk is the intermediate band. Its biconcave shape allows it to be positioned over the anterosuperior aspect of the condyle and along the articular eminence and conform to the condyle. No capsular attachments are located in this region of the articular disk; however, the medial and lateral collateral ligaments do originate from this region. The intermediate band, along with the medial and lateral collateral ligaments, allows the disk to rotate anteriorly and posteriorly on the condyle without being displaced anterior to the condyle. The posterior band is the thickest portion of the articular disk; it is positioned superior on the condyle and in the mandibular fossa during centric occlusion. The posterior superior portion of the disk attaches to the postglenoid spine via the superior stratum, and the posterior inferior aspect of the disk attaches onto the neck of the mandibular condyle via the inferior stratum. The superior stratum is composed primarily of elastic fibers, whereas the inferior stratum is mainly collagenous fibers. Posteriorly, the superior stratum attaches to the tympanic plate, which is stretched with forward translation of the condyle and the disk. The inferior stratum is attached to the condyle posteriorly, which serves to limit further forward displacement of the disk during forward translation. Between these layers of strata is the highly vascular retrodiscal pad. During forward translation of the condyle, the volume of the retrodiscal tissue expands and fills the mandibular fossa and then returns to its original shape and size during closure.
The TMJ is surrounded by a capsule composed of fibrous connective tissue. The capsule has attachments superiorly to the temporal bone and inferiorly to the neck of the condyle and blends mediolaterally with a thickening in the capsule that forms the medial and lateral collateral ligaments. Superiorly, the capsule does not have a medial or lateral attachment to the disk; posteriorly, it attaches to the postglenoid spine; and anteriorly, it blends with the upper and lower heads of the lateral pterygoid muscle and to the disk. The synovial capsule provides nutrients to the avascular regions of the joint. The capsule, lateral collateral ligaments, and posterior attachment are highly innervated with mechanoreceptors and nociceptors that provide kinesthetic and perceptional joint sense, but the disk and synovial tissue are void of receptors. Although all four types of mechanoreceptors are present, type II is the most prominent, followed by type I receptor in the joint capsule (see Table 24-2 for a summary of mechanoreceptor classification). Cranial nerve V supplies innervation to this region via the deep temporal, masseteric, and auriculotemporal nerves, which are branches of the mandibular division.
Temporomandibular Ligaments
Four main ligamentous structures support the TMJ: the lateral ligament (TMJ ligament), internal ligament (sphenomandibular ligament), stylomandibular ligament, and anterior malleolar ligament. The TMJ ligament is a fan-shaped ligament that strengthens the lateral capsule; it originates from the lateral surface of the zygomatic arch and articular eminence and inserts onto the posterolateral portion of the neck of the mandible ( Fig. 15-4 ). This ligament resists excessive retrusion of the mandible and compression of the posterior tissues of the joint; prevents separation of the condyle, disk, and temporal fossa; and assists in the transition from condylar rotation to condylar translation. The ligament is believed to work in synchrony with the surrounding musculature during arthrokinematic transition from condylar rotation to the translation that occurs during mandibular opening. Translation is achieved by tension placed on the oblique portion of the TMJ ligament at approximately 10 mm of opening as the condyle rotates posteriorly and the neck of the condyle moves posteriorly. Therefore, for additional opening to take place, the condyle must translate anteriorly, which decreases tension on the TMJ ligament.
The sphenomandibular and stylomandibular ligaments are extracapsular ligaments ( Fig. 15-5 ). The sphenomandibular ligament runs from the spine of the sphenoid, blends with the medial capsule, and inserts into the lingual aspect of the mandible at the mandibular foramen. The stylomandibular ligament originates from the styloid process of the temporal bone and inserts into the posterior medial angle of the ramus. The exact roles of these ligaments are uncertain, but they may help protect the TMJ during wide excursion. Individually, it is thought that the sphenomandibular ligament may help maintain congruency of the condyle, disk, and temporal bone whereas the stylomandibular ligament may restrict anterior translation of the mandibular condyle.
The anterior malleolar ligament extends from the neck of the malleus and inserts into the medial-posterior-superior aspect of the capsule or the meniscus of the TMJ. Because of its close approximation to the sphenomandibular ligament, tension on this ligament or the medial capsule causes movement of the chain of ossicles and the tympanic membrane. Tension on the anterior malleolar ligament can be caused by either tension from the sphenomandibular ligament at the end range of jaw movement or tension on the medial capsule as a result of disk displacement. This tension on the anterior malleolar ligament is thought to give rise to middle ear symptoms.
Innervation
The TMJ receives innervation from both primary specific articular nerves and multiple accessory articular nerves from the adjoining musculature. The mandibular nerve, which is a division of the trigeminal nerve, has two branches that provide the primary innervation to the TMJ. The posterior attachment and the posterior and lateral joint capsule are supplied by the auriculotemporal nerve, the anterior and anterolateral capsule is innervated by the masseteric nerve, and the posterior deep temporal nerve innervates the anteromedial and medial aspect of the capsule, as well as the deep and superficial temporalis muscle.
Temporomandibular Joint Musculature
The cervical spine plays an important role in the biomechanics and function of the TMJ; therefore, it is important for the rehabilitation specialist to have a through understanding of its function and relationship to the TMJ. The focus in this section of the chapter is on the skeletal muscles involved in mandibular movement and function. Table 15-1 lists these muscles, including the origin, insertion, action, and innervation of each muscle.
| Muscle | TMJ Musculature | Innervation | ||
|---|---|---|---|---|
| Origin | Insertion | Action | ||
| Buccinator | Alveolar processes of the maxilla, buccinator ridge of the mandible, and pterygomandibular ligament | Orbicularis oris at the angle of the mouth | Compresses the cheeks against the teeth, aids in whistling and smiling, assists in mastication | Buccal branch of the facial nerve (cranial nerve VII) |
| Orbicularis oris | Strata of the muscular fibers surrounding the orifice of the mouth | Skin and mucous membrane of the lips; blends with the surrounding muscles | Compresses the lips against the teeth; brings the lips together | Buccal and mandibular branches of the facial nerve (cranial nerve VII) |
| Masseter | Superficial : Zygomatic process of the maxilla and anterior two thirds of the lower border of the zygomatic arch Middle: Anterior two thirds of the deep surface of the zygomatic arch and lower border of the zygomatic arch Deep: Deep surface of the zygomatic arch | Superficial: Angle and lower, lateral surface of the ramus of the mandible Middle: Middle of the ramus of the mandible Deep: Upper ramus of the mandible and coronoid process | Initiates elevation of the mandible and adds force to closure; contributes to clenching during emotional stress and nocturnal clenching and bruxing; assists in protraction and lateral deviation | Masseteric nerve from the mandibular division of the trigeminal nerve |
| Temporalis | Temporal fossa, deep surface of the temporal fascia | Coronoid process of the mandible and anterior border of the ramus of the mandible; some fibers insert into the skeletal orbit of the eye | Elevates the mandible; unilaterally deviates to the ipsilateral side; retracts the mandible from a protracted position | Deep temporal branch of the mandibular nerve |
| Lateral pterygoid | Superior head: Greater wing of the sphenoid bone Inferior head: Lateral surface of the lateral pterygoid plate | Anterior head of the mandibular head, articular capsule, and TMJ disk | Opens and protrudes the mandible, pulls the disk forward, and assists in the rotary motion of chewing; acts with the medial pterygoid to move the jaw side to side Superior head: Eccentrically controls the disk with a backward glide during closure Inferior head: Translates the mandibular head downward with opening | Lateral pterygoid branch of the mandibular nerve |
| Medial pterygoid | Palatine bone and tuberosity of the maxilla | Medial surface of the ramus and mandibular angle | Elevates the mandible; protrudes the jaw; unilaterally deviates the mandible contralaterally | Medial pterygoid branch of the mandibular division of the trigeminal nerve |
| Digastric | Posterior belly: Mastoid notch of the temporal bone Anterior belly: Digastric fossa of the mandible | Greater cornu and body of the hyoid bone by a fibrous loop midway along the body of the mandible | Depresses the mandible; elevates the hyoid | Posterior: Facial nerve Anterior: Mylohyoid branch of the mandibular division of the trigeminal nerve |
| Stylohyoid | Posterior surface of the styloid process | Body of the hyoid bone at the juncture with the greater cornu | Elevates and draws the hyoid back to elongate the floor of the mouth; fixes the hyoid for the tongue muscles | Mylohyoid branch of the inferior alveolar division of the mandibular nerve |
| Mylohyoid | Mylohyoid line of the mandible | Hyoid bone and median fibrous raphe | Elevates the floor of the mouth; elevates the hyoid bone; depresses the mandible | Mylohyoid branch of the inferior alveolar division of the mandibular nerve |
| Geniohyoid | Inferior mental spine on the back of the symphysis menti | Anterior surface of the hyoid bone | Elevates the hyoid; with the hyoid fixed, depresses the mandible | C1 via the hypoglossal nerve |
| Sternohyoid | Posterior medial surface of the clavicle, posterior sternoclavicular ligament, upper and posterior manubrium sterni | Inferior body of the hyoid | Depresses the hyoid, assists in speech and mastication | Ansa cervicalis (C1-C3) |
| Sternothyroid | Posterior surface of the manubrium sterni and cartilage of the first rib | Oblique line, lamina of the thyroid cartilage | Draws the larynx down after it has been elevated | Ansa cervicalis (C1-C3) |
| Thyrohyoid | Oblique line, lamina of the thyroid cartilage | Lower border of the greater cornu and adjacent body of the hyoid | Depresses the hyoid; elevates the larynx | C1, C2 fibers from the hypoglossal nerve |
| Omohyoid | Upper border of the scapula near the scapular notch | Inferior belly: Intermediate tendon Superior belly: Lower border of the hyoid | Depresses and elevates the hyoid; may assist in inspiration | Inferior belly: Ansa cervicalis (C2-C3) Superior belly: Superior root of the ansa cervicalis (C1) |
Biomechanics
The TMJ is a synovial ginglymoarthrodial joint with osteokinematic motions that are described as depression, elevation, protrusion, retrusion, and lateral excursion. The arthrokinematic movements can be divided into active accessory and passive accessory movements. Active accessory movements are a result of muscle contraction and include translation, rotation, compression, and spin. Passive accessory movements (joint play) include distraction and lateral glide. In addition to these accessory motions, rotary movements occur between the head of the condyle and the disk during mandibular opening and closing. During mandibular opening, rotation occurs between the disk and condylar head with concomitant translation occurring between the disk and temporal bone ( Fig. 15-6 ).
Mandibular depression occurs as a result of condylar rotation during the first 10 mm of opening; the neck of the condyle moves posteriorly and places tension on the TMJ ligament. As the TMJ ligament checks rotatory motion, additional movement occurs as the inferior belly of the lateral pterygoid induces anterior translation of the condylar head for approximately 10 mm, after which rotation and translation occur together until functional opening takes place. Mandibular protrusion occurs as a result of condylar translation, whereas mandibular lateral deviation is produced by condylar translation contralaterally and condylar spin ipsilaterally.
Although the disk is firmly attached to the head of the condyle, they rotate independently of one another with mandibular movement. During the initial 10 mm of mandibular opening the condyle rotates on a relatively stationary disk, followed by anterior translation of both the condyle and disk. However, because of the “self-seating” disk-to-condyle relationship and the tension that develops at the posterior attachment, a relative posterior rotation occurs between the disk and the condyle after the initial 10 mm of opening. Conversely, during mandibular closing, although both the condylar head and disk translate posteriorly, the disk rotates relatively anteriorly on the condyle because of the conforming “self-seating” disk-to-condyle articulation and tension in the lateral pterygoid ( Fig. 15-7 ). During normal movement, the disk and condyle move forward approximately 7 and 14 mm, respectively.
Evaluation
“The interdependency of the cranium, cervical and thoracic spine, and TMJ requires that the interaction between these components be considered as one functional, intricately-balanced unit”—Ola Grimsby, PT, DMT, FFAAOMPT.
Evaluation of the TMJ is warranted in patients with complaints of headache or maxillofacial, cervicogenic, or shoulder girdle pain because of the common referral patterns of the TMJ. When pathology in the TMJ is suspected, the sports rehabilitation specialist should assess the cervical and thoracic spine and the shoulder girdle because of the attachment of the surrounding musculature, as well as the biomechanical relationship of these joint systems. This can be illustrated with the common head forward/rounded shoulder posture, which as a result of increased tension placed on the hyoid muscles and a relative posterior position of the mandible, gives rise to retracted malocclusion in the sagittal plane. In addition, a dysfunction such as scoliosis causes the upper cervical spine to compensate and “right” the cranium in the horizontal plane. This corrected compensation is achieved by upper cervical side bending with concomitant contralateral rotation, which results in the frontal plane occlusion of a crossbite.
Box 15-1 outlines the sequence of examination. A systematic approach to the evaluation process is helpful to ensure that the clinician does not overlook any step in the assessment and that the examination flows smoothly. By performing all the elements of the evaluation listed in Box 15-1 , the sports rehabilitation specialist will be able to determine which tissues are involved from their response to the tests imposed. Each tissue is suspected as being a potential source of the pain ( Fig. 15-8 ) until the tissue has been cleared by careful examination. To clear a tissue, the examiner must perform tests that create stress or tension on that tissue. If a positive response does not occur, the tissue can be excluded as a source of the pain.
Initial observation
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Posture of the head and cervical spine
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Mouth movement with speaking
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Personality and attitude of the athlete
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Patient’s subjective history
Structural inspection
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Anterior/posterior/lateral
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Standing/sitting position
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Assessment of the vertical and horizontal alignment of head position
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Oral inspection
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Respiration pattern
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Quick tests of the cervical spine to rule out pathology
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Active motion (assess range, speed, quality, aberrations in movement, clicking)
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Mandibular opening (40 mm)
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Lateral deviation (1 tooth wide, 8 mm)
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Mandibular protrusion
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Mandibular retrusion
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Teeth clinching
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Bilateral molar biting on a cotton roll (joint distraction)
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Unilateral molar biting on a cotton roll (ipsilateral distraction, contralateral compression)
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Passive motion
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Vertical opening
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Lateral movements
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Retraction
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Protraction
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Resisted motion (each motion tested in a neutral position)
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Mandibular depression
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Mandibular elevation
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Lateral deviation
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Retrusion
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Protrusion
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Palpation (note variations in temperature, atrophy, swelling, tenderness, thickness, dryness, moisture, abnormalities, crepitus, and pain)
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Crepitation, grinding, clicking with mandibular movement
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Temporomandibular ligament
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Posterior glenoid spine
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Medial/lateral pterygoid muscle
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Temporalis muscle
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Anterior and posterior digastric muscle
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Occipital nerve
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Neurologic tests
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Sensation tests
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Reflexes
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Mandibular
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Biceps/triceps/brachioradialis/abductor digiti minimi
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Myotomes
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Cranial nerve testing (I to XII)
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Special tests
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Chvostek
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Mobility tests
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Distraction
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Anterior glide
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Lateral glide
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Diagnostic tests
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Radiographs, magnetic resonance imaging, computed tomography, myelography, electromyography, laboratory tests
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Initial Observation
The examination process begins with initial observation of the athlete. The clinician watches the athlete walk into the room and observes the position of the head, neck, and shoulder girdle. The sports rehabilitation specialist should observe the way the athlete speaks and develop an understanding of how the dysfunction is affecting the athlete’s functional ability.
History
The athlete’s subjective history is a crucial part of the evaluation process. A complete and thorough history allows the sports rehabilitation specialist to determine the causative factors locally, regionally, or globally, as well the direction and goal of treatment. In addition to a general history, Box 15-2 contains some specific information the clinician should obtain.
Does the athlete have any pain with activities such as chewing, talking, yawning, biting, swallowing, or shouting?
Was any injury associated with this condition?
Does the athlete have any pain with the mouth fully opened or during biting?
Does the athlete have any complaints of clicking when opening the jaw, or does the jaw ever lock in place?
Does the athlete grind the teeth, clench the jaw, have any painful or sensitive teeth, or have any difficulty swallowing?
Does the athlete awaken in the morning with pain or soreness in the TMJ or surrounding musculature?
Has the athlete had any ear problems such as ringing, earaches, dizziness, or feeling faint?
Does the athlete have a history of headaches and if so in what location?
Does the athlete have any habitual or postural habits that can add stress to the TMJ, such as nail biting, chewing gum, smoking, leaning on the chin, or holding a telephone between the shoulder and ear?
Has the athlete ever undergone any previous treatment of this condition and what was the outcome of this treatment?
Has any diagnostic tests such as radiography or magnetic resonance imaging been performed?
TMJ, Temporomandibular joint.
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