The Temporomandibular Joint – Structure – Function

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Original Author(s): Oliver Jones
Last updated: January 19, 2023
Revisions: 33

Original Author(s): Oliver Jones
Last updated: January 19, 2023
Revisions: 33

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• 1 Articulating Surfaces
• 2 Ligaments
• 3 Movements
• 4 Neurovascular supply
• 5 Clinical Relevance: Temporomandibular Joint Dislocation

The temporomandibular joint (TMJ) is formed by the articulation of the mandible and the temporal bone of the cranium. It is located anteriorly to the tragus of the ear, on the lateral aspect of the face.

In this article, we shall look at the anatomy of the temporomandibular joint – its articulating surfaces, ligaments and clinical correlations.

Articulating Surfaces

The temporomandibular joint consists of articulations between three surfaces; the mandibular fossa and articular tubercle (from the squamous part of the temporal bone), and the head of mandible.

This joint has a unique mechanism; the articular surfaces of the bones never come into contact with each other – they are separated by an articular disk. The presence of such a disk splits the joint into two synovial joint cavities, each lined by a synovial membrane. The articular surface of the bones are covered by fibrocartilage, not hyaline cartilage.

By TeachMeSeries Ltd (2023)

Fig 1 – The osteology of the temporomandibular joint

Ligaments

There are three extracapsular ligaments. They act to stabilise the temporomandibular joint.

• Lateral ligament – runs from the beginning of the articular tubule to the mandibular neck. It is a thickening of the joint capsule, and acts to prevent posterior dislocation of the joint.

• Sphenomandibular ligament – originates from the sphenoid spine, and attaches to the mandible.

• Stylomandibular ligament – a thickening of the fascia of the parotid gland. Along with the facial muscles, it supports the weight of the jaw.

By TeachMeSeries Ltd (2023)

Fig 2 – The joint capsule and accessory ligaments of the temporomandibular joint.

Movements

Movements at this joint are produced by the muscles of mastication, and the hyoid muscles. The two divisions of the temporomandibular joint have different functions.

Protrusion and Retraction

The upper part of the joint allows protrusion and retraction of the mandible – the anterior and posterior movements of the jaw.

The lateral pterygoid muscle is responsible for protrusion (assisted by the medial pterygoid), and the posterior fibres of the temporalis perform retraction. A lateral movement (i.e. for chewing and grinding) is achieved by alternately protruding and retracting the mandible on each side.

Elevation and Depression

The lower part of the joint permits elevation and depression of the mandible; opening and closing the mouth. Depression is mostly caused by gravity. However, if there is resistance, the digastric, geniohyoid, and mylohyoid muscles assist. Elevation is very strong movement, caused by the contraction of the temporalis, masseter, and medial pterygoid muscles.

Neurovascular supply

The arterial supply to the TMJ is provided by the branches of the external carotid, principally the superficial temporal branch. Other contributing branches include the deep auricular, ascending pharyngeal and maxillary arteries.

The TMJ is innervated by the auriculotemporal and masseteric branches of the mandibular nerve (CN V3).

Clinical Relevance: Temporomandibular Joint Dislocation

A dislocation of the temporomandibular joint can occur via a blow to the side of the face, yawning, or taking a large bite. The head of the mandible ‘slips’ out of the mandibular fossa, and is pulled anteriorly.

The patient becomes unable to close their mouth. The facial and auriculotemporal nerves run close to the joint, and can be damaged if the injury is high-energy.

Posterior dislocations of the TMJ are possible, but very rare, requiring a large amount of force to overcome the postglenoid tubercle and strong intrinsic lateral ligament.

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Westerville, OH Dentist – Westerville, OH Dentist

The temporomandibular joint (TMJ) is the joint connecting the lower jaw (mandible)
to the skull (temporal bone). The lower jaw and the skull are connected by
a number of muscles and ligaments, which function in harmony with each other
if the lower jaw is in the correct position. The head of the jaw bone (lower
jaw) is called the condyle and it fits into the concavity of the temporal
bone called the glenoid fossa. The TM joint resembles a ball and socket with
the round condyle being the ball and the glenoid fossa of the temporal bone
being the socket. For normal joint function to occur, a piece of cartilage
called an articular disc acts as a cushion or shock absorber between the
two bones.

NORMAL JAW JOINT

click to enlarge

When the lower jaw opens and closes, the disc stays between
the condyle and the glenoid fossa of the temporal bone at all times. When
this happens, this is a normal healthy TMJ and the patient can open wide
without any discomfort and without any noise. With a normal opening, the
patient should be able to get three fingers between the upper and lower front
teeth when the mouth is open as wide as possible. In cases where the TM joint
is functioning normally with the disc in the proper position, the muscles
of the head, neck and shoulders function relatively pain-free.

What is TMD?

Temporomandibular disorder (TMD) is the condition
referring to a joint that is not normal.

The position of your teeth can affect the position
of your jaw joints. Each jaw joint is a ball and socket joint. When functioning
properly, the ball and socket do not actually touch because a thin disc of
cartilage rides between them. The disc acts as a cushion and allows the joint
to move smoothly. Each disc is held in place and guided by muscles and ligaments.
If your bite is not right, as in cases where the following may occur: deep
overbite, lower jaw too far back, narrow upper jaw or upper front teeth crooked
and tipped backwards, this can cause the jaw to become dislocated. Typically
the disc is pulled forward. The lower jaw then has a tendency to go back
too far and the top of the lower jaw, which resembles a ball (condyle), presses
on the nerves and blood vessels at the back of the socket and causes pain.

Usually, the protective disc (cartilage) is displaced
forward and no longer serves as a cushion between the condyle (lower jaw)
and the bony socket (skull) and eventually this can lead to the condyle rubbing
against the bony socket. This can cause a problem called osteoarthritis.

Mild displacements cause a clicking or popping
sounds in the jaw joint.

When the disc becomes displaced, this is what causes
the various noises within the jaw joints such as clicking and popping sounds.
Patients must be aware that any noises or pain that occur during the opening
and closing of the jaw is an indication that the jaw joints have become dislocated.
Patients are advised to seek treatment as soon as possible to avoid allowing
the problem to get worse.

More severe displacement can be very painful and
eventually can cause permanent damage to the joint. An unstable bite can
cause both jaw joint displacement and muscle strain and pain. Many seemingly
unrelated symptoms results, which are collectively known as craniomandibular
dysfunction. These symptoms include headaches, neck aches, ringing in the
ears, stuffiness in the ears, pain behind the eyes, ear pain, shoulder and
lower back pain, dizziness and fainting, difficulty swallowing, and tingling
of the fingers and hands. These symptoms include:

• Headaches
• Neck aches
• Ringing in the
  ears
• Stuffiness in
  the ears
• Pain behind the
  eyes
• Ear pain
• Shoulder and
  lower back pain
• Dizziness and
  fainting
• Difficulty swallowing
• Tingling of the
  fingers and hands

Photo of Degenerative Joint Disease and Degenerative Joint

Articular surface – Temporal bone – Temporomandibular joint – vet-Anatomy

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Gallery

Comparative human anatomy

• Articular surface

Translations

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Diseases of the temporomandibular joint | Face Smile Multidisciplinary Clinic Center

December 1, 2020

Various pathologies of the temporomandibular joint are a fairly common phenomenon that significantly affects the patient’s standard of living. The TMJ performs many important functions such as swallowing, speaking, and chewing food. The joint is responsible for opening and closing the mouth, for the movements of the lower jaw. Next, we will consider what abnormalities include TMJ pathologies, what are the main complaints of patients and in which cases TMJ prosthetics are necessary.

TMJ pathologies

The temporomandibular joint (articulatio temporomandibular) is a paired joint at the junction of the skull and lower jaw. The TMJ is formed by the articulation of the mandibular fossa of the temporal bone and the head of the mandible. This is the only movable part of the skull that performs a large number of complex functions . As mentioned above, the joint provides movement of the lower jaw up and down, right and left, forward and backward, allows a person to close and open his mouth, is responsible for the formation of speech, singing, chewing and swallowing.

Today, TMJ diseases occur in a fairly large number of patients. Since the jaw joint is a complex functional system, its pathology can be multidisciplinary in nature and in some cases requires the joint work of specialists from various fields from maxillofacial surgery to neurology.

Consider the main types of TMJ diseases

• Musculo-articular dysfunction of the TMJ . It is a disorder of the function of the masticatory muscles of the joint and a violation of the relative position of the elements of the TMJ.
• Arthrosis of the TMJ . A disease of a dystrophic nature, expressed in progressive degenerative changes in the joint, narrowing of the joint space and impaired activity of the masticatory muscles.
• TMJ arthritis . Inflammatory disease of the temporomandibular joint, which develops with injuries, allergic reactions, infections. The picture includes various destructive changes in the form of expansion or narrowing of the joint space, osteoporosis.
• Dislocation and subluxation of the head of the joint . It is expressed in the exit of the articular head beyond the glenoid fossa of the temporal bone as a result of a violation of the relative position of the elements of the TMJ.
• Articular disc lesions . A common pathology of the TMJ, manifested in the deviation of the position of the articular disc from the norm, its displacement.
• TMJ ankylosis . A pronounced violation of the mobility of the TMJ, which can be both congenital and acquired. With ankylosis, there is an fusion of the articular surfaces, leading to a partial or even complete lack of mobility in the joint.

Among the causes of the listed pathologies , various factors can be indicated, including the effects of infections, autoimmune diseases and connective tissue diseases (in the case of arthritis). Endocrine disorders and injuries (arthrosis) can also affect the health of the TMJ. Acute and chronic diseases of the TMJ, purulent processes, osteomyelitis, rheumatoid disease and joint fractures can lead to ankylosis. Occlusal disorders, psycho-emotional factors, unsuccessful prosthetics and even unsuccessful eruption of wisdom teeth or other pathologies of the dentition can cause musculo-articular dysfunction. Occlusion pathologies, poor-quality prosthetics and mechanical injuries of the joint can also lead to displacement of the articular disc and dislocations.

Symptoms of TMJ pathology

Symptoms of TMJ diseases include a large number of very different manifestations from painful sensations and unpleasant sounds to difficulty opening and closing the mouth. Consider the main signs that allow you to determine the pathology of the TMJ.

• Pain syndrome . Pain can be localized not only in the area of ​​​​the joint itself, but also spread to the head, temple area, and cervical region. Some patients may complain of soreness in the ears, heaviness in the head, pressure and pain in the eye area. Discomfort can manifest itself in a calm state and at the time of movement of the lower jaw.
• Impaired mobility . The restriction of the TMJ motion is also called “blocking”, “locking”, “jamming” of the joint. When the joint is blocked, the patient notes difficulty in opening and closing the mouth. The structures of the articular joints act in violation, so the movements of the joint are uneven, it seems to “get stuck”, catching the optimal position.
• Sound signs . Clicking, crunching, crackling is one of the most common complaints among patients with TMJ pathologies. Crepitus (a characteristic crackling sound) occurs when the mouth is opened wide (for example, when yawning), chewing food, and even when swallowing. In some cases, the sound is so expressive that it can be heard from the side.
• Other symptoms . In the pathology of the TMJ, other manifestations of the disease also make themselves felt: disturbed sleep, snoring, dizziness, bruxism. The presence of swelling and pain on palpation may indicate the acute form of the disease and the development of the inflammatory process.

The method of examining patients with pathologies of the TMJ includes, first of all, the study of complaints, palpation (a physical method of medical diagnosis, carried out by feeling the area under study) and auscultation (a diagnostic method that consists in listening to sounds generated during the functioning of the organ under study) of the joint area .

Diagnosis of TMJ pathologies

The initial examination begins with a detailed analysis of the patient’s complaints, the collection of a detailed history and external examination. The doctor pays attention to the symmetry and relationship of facial proportions , evaluates the appearance of the articular area for swelling or hyperemia, which may indicate the presence of edema and an acute inflammatory process. The specialist also examines the oral cavity and analyzes the degree of mouth opening , evaluates the mobility of the lower jaw , determines the type of bite and looks at the defects of the dentition (sometimes even poor-quality fillings or unsuccessful prostheses can affect the state of the TMJ, provoking its overload).

This is followed by palpation and auscultation of the problem area. The doctor studies the condition of the masticatory muscles and tissues in the TMJ area, evaluates pain , looks at the position of the articular heads . Listening to the sounds accompanying the movement of the joint is also an important part of the diagnosis, since crepitus often accompanies TMJ pathologies. In some cases, casts are taken for the manufacture of diagnostic plaster models of the jaws, which allow assessing the closure of the dentition and bite, occlusionograms are performed (a relief impression of the occlusal contacts of the dentition on a wax plate).

The variety of clinical manifestations of pathologies of the temporomandibular joint in some cases requires special X-ray studies. A TMJ x-ray, CT scan, or MRI may be done to evaluate the condition of the joint. These studies, together with the results of examination and analysis of models, provide detailed data on the degree of destructive changes and the nature of pathological processes in the joint.

Treatment of TMJ pathologies

The doctor selects the treatment regimen for each patient individually, depending on the type of disease . In acute pain, in order to relieve symptoms, the patient may be advised to reduce the load on the joint (eating soft food, limiting chewing and speech load). The main treatment should always be carried out taking into account the causes of the pathology .

TMJ treatment may vary from conservative dental and medical treatment to complex surgical procedures . Depending on the type of pathology, treatment may include a short course of anti-inflammatory, analgesic, and muscle-relaxing drugs. Also, in some cases, the use of special mouth guards, plates, splint therapy, massage, myogymnastics or an orthopedic treatment method with selective grinding of teeth may be indicated. In the fight against certain pathologies, the use of physiotherapy can be effective, in other cases, the work of a specialist may be required to work out stress and relax the masticatory muscles. In cases with dislocations, the jaw is set and temporarily immobilized with an elastic bandage. In cases of musculo-articular dysfunctions, effective treatment may lie in proper prosthetics or in competent bite correction.