TMJ anatomy: the temporomandibular joint, its disc, ligaments and movements

The temporomandibular joint is the synovial joint between the mandible and the temporal bone. It lies in front of the tragus of the ear, and its surfaces are the mandibular fossa and articular tubercle of the squamous temporal bone above and the head of the mandible below. The bones never touch each other directly, because an articular disc lies between them. (TeachMeAnatomy: The Temporomandibular Joint.)

Everyone has two temporomandibular joints, one on each side of the jaw. You can feel them by placing your fingers just in front of your ears and opening your mouth. TMJ is the name of the joint itself; temporomandibular disorders (TMD) are the conditions that cause pain or dysfunction in it. (National Institute of Dental and Craniofacial Research: TMD (Temporomandibular Disorders).)

The TMJ is classified as a ginglymoarthrodial joint, a name that combines ginglymus (a hinge joint) and arthrodia (a gliding joint). The lower part of the joint hinges as the jaw opens and closes, while the upper part lets the condyle glide forwards and backwards between the fossa and the articular tubercle. (Elsevier Complete Anatomy: Temporomandibular joint.)

The upper part of the joint is formed by the temporal bone. The mandibular fossa is the deep, oval depression on the outer base of the skull, and the articular tubercle (articular eminence) is the smooth ridge immediately in front of it. The lower part is the condylar process of the mandible, the back projection of the ramus, which is topped by the oval condyle. The more anterior projection of the ramus is the flattened coronoid process. (OpenStax Anatomy and Physiology 2e, 7.2: The Skull.)

Unlike most synovial joints, whose surfaces are covered with hyaline cartilage, the TMJ surfaces are covered by fibrocartilage. Elsevier's anatomy notes point out that fibrocartilage is better able to withstand high forces, which suits a joint that carries chewing loads. (Elsevier Complete Anatomy: Temporomandibular joint.)

A small bony lip at the back of the fossa, the postglenoid tubercle, works with the strong lateral ligament to make posterior dislocation of the jaw very rare: a large force is needed to overcome them. (TeachMeAnatomy: The Temporomandibular Joint.)

The squamous, petrous, tympanic and mastoid parts, including the mandibular fossa. Temporal bone.

The articular disc is a biconcave plate of fibrocartilage, thin in the centre and thick around its edge. In side view it looks like a bow tie: a thick anterior band and a thick posterior band joined by a thin intermediate zone. It is tilted forwards by 10 to 30 degrees from the horizontal, attaches in front to the joint capsule, and is tied at its sides to the medial and lateral poles of the condyle. (Radiopaedia: Temporomandibular joint.)

With the mouth closed, the junction between the posterior band and the tissue behind it sits near the 11 or 12 o'clock position on top of the condyle. Radiologists call the disc anteriorly displaced when this junction lies further forwards, or when the posterior band is more than 10 degrees from the vertical line through the condyle. (Oliveira LRLB et al. Temporomandibular joint: from anatomy to internal derangement. Radiol Bras 2023.)

The disc is attached to the inner surface of the capsule and separates the joint surfaces completely. It stabilises the condyle, reduces friction and may help lubrication. The articular tissues and the dense part of the disc have no nerve supply. (Kenhub: Temporomandibular joint.)

Behind the disc, the posterior band splits into two layers: an upper fibroelastic lamina and a lower fibrous lamina. Between them is the loose, richly innervated, vascular retrodiscal (interlaminar) tissue, also called the bilaminar zone. It is best seen on MRI with the mouth open. (Radiopaedia: Temporomandibular joint.)

The upper layer, the temporal lamina, inserts into the front of the external auditory canal, and the lower layer inserts into the back of the condyle. Together they stop the disc slipping or rotating too far. (Oliveira LRLB et al. Temporomandibular joint: from anatomy to internal derangement. Radiol Bras 2023.)

The external acoustic meatus and middle ear that lie just behind the TMJ. Ear anatomy.

The fibrous capsule arises from the borders of the mandibular fossa, encloses the articular tubercle, and attaches below to the neck of the mandible, just above the pterygoid fovea. It is loose, which allows the mandible to move forwards a long way without tearing capsular fibres. (Kenhub: Temporomandibular joint.)

Radiopaedia describes the capsule as loose above the disc, reaching the edges of the articular surface of the fossa so that the condyle can translate forwards, and tight below the disc, anchoring it to the condylar neck so that disc and condyle move together. (Radiopaedia: Temporomandibular joint.)

The disc divides the joint into two synovial spaces, each lined by its own synovial membrane. The upper (discotemporal) space, between the disc and the temporal bone, allows gliding: protrusion, retraction and side-to-side movement. The lower (discomandibular) space, between the disc and the condyle, allows rotation for opening and closing. (Radiopaedia: Temporomandibular joint.)

The lateral ligament, also called the temporomandibular ligament, is an intrinsic ligament: a thickened part of the capsule that strengthens the joint on its lateral side. Together with the postglenoid tubercle it prevents posterior dislocation. Kenhub describes the two other ligaments as extrinsic and says they give no significant support to the joint, although the sphenomandibular ligament acts as a swinging hinge for the mandible. (Kenhub: Temporomandibular joint.)

The sphenomandibular ligament descends from the spine of the sphenoid bone to the lingula on the inner surface of the ramus. It is pierced by the nerve to mylohyoid, and the auriculotemporal nerve and inferior alveolar vessels pass between it and the neck of the mandible. Radiopaedia calls it, with the muscles of mastication, the primary passive support of the mandible. (Radiopaedia: Sphenomandibular ligament.)

The stylomandibular ligament runs from the styloid process to the angle of the mandible. TeachMeAnatomy describes it as a thickening of the fascia of the parotid gland which, with the facial muscles, supports the weight of the jaw. The same page traces the lateral ligament from the articular tubercle to the neck of the mandible. (TeachMeAnatomy: The Temporomandibular Joint.)

The mandible can be depressed, elevated, moved forwards and backwards, and moved slightly from side to side. IMAIOS explains that small openings, such as in ordinary speech, use only the lower joint, which works like a hinge. Wider opening also brings in the upper joint, where the disc and condyle glide forwards onto the articular tubercle. (IMAIOS e-Anatomy: Temporomandibular joint.)

The axis of rotation lies a little below the centre of the condyle, at the level of the insertion of the temporomandibular ligament. When the mouth opens fully, the condyle moves forwards with the disc and comes to lie beneath the articular eminence. (Radiopaedia: Temporomandibular joint.)

In real chewing and talking the two kinds of movement are combined rather than separate: rotation and translation usually happen at the same time. Rotation in the lower space can occur around axes in all three planes. (Kenhub: Temporomandibular joint.)

Side-to-side grinding is not a separate movement of its own. It is produced by alternating protrusion and retraction of the mandible on each side. (TeachMeAnatomy: The Temporomandibular Joint.)

Maximal mouth opening is measured between the edges of the upper and lower incisors. In a study of 894 healthy Indian adults aged 21 to 70, the average was 51.3 mm in men and 44.3 mm in women, and opening became smaller with age in both sexes. (Khare N et al. Normal Mouth Opening in an Adult Indian Population. J Maxillofac Oral Surg 2012.)

A 2025 study of 400 Saudi adults found an average of 45.7 mm (47.9 mm in men and 44.3 mm in women) and reviewed studies of other populations, most of which report averages between about 40 and 55 mm. The authors note that trismus, restricted mouth opening, is commonly defined as a maximal opening of less than 35 mm. (Almohaimeed B, Ikram R. The association between maximum mouth opening and sociodemographic factors among Saudi adults. Front Oral Health 2025.)

The TMJ is moved by the muscles of mastication and the hyoid muscles. Elevation, the strong closing movement, is produced by temporalis, masseter and the medial pterygoid. Depression is mostly due to gravity, helped by the digastric, geniohyoid and mylohyoid against resistance. Protrusion is by the lateral pterygoid, assisted by the medial pterygoid, and retraction by the posterior fibres of temporalis. (TeachMeAnatomy: The Temporomandibular Joint.)

The lateral pterygoid has a special relationship with the joint. Its upper fibres insert into the capsule and disc and its lower fibres into the pterygoid fovea on the condylar neck, so it pulls the disc and condyle forwards. Radiopaedia notes that the exact roles of the masticatory muscles in TMJ movement, and the lateral pterygoid's part in dysfunction, are still debated. (Radiopaedia: Temporomandibular joint.)

Masseter, temporalis and the medial and lateral pterygoids in detail. Muscles of mastication.

The TMJ receives blood mainly from branches of the external carotid artery, especially the superficial temporal artery, with contributions from the deep auricular, ascending pharyngeal and maxillary arteries. Its nerves are the auriculotemporal and masseteric branches of the mandibular nerve (V3), the third division of the trigeminal nerve. (TeachMeAnatomy: The Temporomandibular Joint.)

Kenhub gives a slightly different emphasis: it names the deep auricular artery, a branch of the maxillary artery, as the main supplier, with the superficial temporal and anterior tympanic arteries, and lists the deep temporal nerves as a minor nerve supply. Veins drain to the superficial temporal and maxillary veins. (Kenhub: Temporomandibular joint.)

The trigeminal nerve and its mandibular division, which supplies the TMJ and the chewing muscles. Cranial nerves.

Temporomandibular disorders are a group of more than 30 conditions that cause pain and dysfunction in the jaw joint and the muscles that move it. The US National Institute of Dental and Craniofacial Research estimates that TMD affects about 5% of US adults and is twice as common in women as in men, especially women aged 35 to 44. Clicking or popping without pain is common and normal. (National Institute of Dental and Craniofacial Research: TMD (Temporomandibular Disorders).)

Symptoms include jaw and face pain, headaches, stiffness or locking of the jaw, and clicking, popping or grinding sounds. Cleveland Clinic notes that TMJ disorders most often begin between the ages of 20 and 40 and that women are about twice as likely to develop them. (Cleveland Clinic: TMJ Disorders.)

A 2023 review gives TMD figures of up to 28% of the general population and names internal derangement, an abnormal relationship between the disc and the condyle, as the main cause of TMJ dysfunction; its signs include joint pain, deviation of the jaw on opening and clicks. The disc can be displaced forwards, backwards, medially or laterally, with recapture (it returns to its place as the mouth opens) or without recapture. Small anterior displacements are seen in up to 33% of people with no symptoms, while displacement without recapture is often linked with a deformed disc, joint effusion or perforation. (Oliveira LRLB et al. Temporomandibular joint: from anatomy to internal derangement. Radiol Bras 2023.)

In a TMJ dislocation the condyle loses contact with the mandibular fossa. Anterior dislocation is by far the most common: the condyle slides forwards over the articular eminence, either through an exaggerated, often recurrent, normal forward movement or through forceful opening of the mouth. Radiopaedia reports that up to 7% of the population dislocate the jaw at some point, most often between 20 and 40 years of age. Cranial dislocation is uncommon: an upward blow fractures the mandibular (glenoid) fossa and the condyle enters the middle cranial fossa. (Radiopaedia: Temporomandibular joint dislocation.)

A dislocated jaw can follow a big yawn, a large bite or a blow to the side of the face, and the person cannot close the mouth. The facial and auriculotemporal nerves run close to the joint and can be damaged in high-energy injuries. Posterior dislocation is very rare because of the postglenoid tubercle and the lateral ligament. (TeachMeAnatomy: The Temporomandibular Joint.)

The 3D viewer highlights the mandible, the temporal bone, the sphenoid and the zygomatic bone in the BodyParts3D model of an adult male. Turn to the left lateral view to find the condylar process sitting in the mandibular fossa just in front of the external acoustic meatus, with the articular eminence in front of it and the coronoid process passing under the zygomatic arch. Look from below to see the spine of the sphenoid, where the sphenomandibular ligament begins. The model has no articular disc, capsule, ligaments or masticatory muscles, so use the diagrams on this page for those. (Mitsuhashi N et al. BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Res 2009.)

The lower jaw bone, its condylar and coronoid processes, ramus and foramina. Mandible.

Mandible

The lower jaw bone.

Sphenoid bone

A butterfly-shaped bone at the base of the skull.

Temporal bone

A paired bone forming part of the side and base of the skull.

Zygomatic bone

The cheekbone.