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Temporomandibular joint.
Last reviewed: 04.07.2025
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The temporomandibular joint (art. temporomandibularis) is the only joint in the skull. This joint is paired, formed by the articular head of the lower jaw, as well as the mandibular fossa and articular tubercle of the temporal bone, covered with fibrocartilage. The joint capsule of this joint is wide. On the temporal bone, it is attached in front of the articular tubercle, and behind - near the petrotympanic fissure. On the condylar process of the lower jaw, the capsule is attached approximately 0.5 cm below the posterior edge of the head of this bone. The joint capsule is fused with the peripheral parts of the articular disc, so the disc divides the joint cavity into two sections (floors) isolated from each other. The synovial membrane of the temporomandibular joint is also divided into the superior and inferior synovial membranes (membranae synoviales superior et inferior), covering the inner surface of the joint capsule of the upper and lower floors of the joint, respectively.
The temporomandibular joint is strengthened by ligaments. Lateral ligament(lig. laterale) is a lateral thickening of the capsule. Outside the joint there are two ligaments. The sphenomandibular ligament(lig. sphenomandibulare) originates on the spine of the sphenoid bone and is attached to the lingula of the mandible. Stylomandibular ligament(lig. stylomandibulare) goes from the styloid process of the temporal bone to the inner surface of the lower jaw, attaching near its angle.
The temporomandibular joint is paired, complex (has an articular disc, discus articularis), combined, ellipsoidal in shape. The following types of movements are performed in the right and left temporomandibular joints: lowering and raising the lower jaw, corresponding to opening and closing the mouth. It is possible to move the lower jaw forward and return to its original position; movement of the lower jaw to the right and left (lateral movements).
When the lower jaw is lowered, the chin protrusion moves downwards and backwards, along an arc with its concavity facing backwards and upwards. Three phases are distinguished in this movement. In the first phase (insignificant lowering of the lower jaw), movement occurs around the frontal axis in the lower floor of the joint. The articular disc remains in the glenoid fossa. In the second phase, with a significant lowering of the lower jaw against the background of the hinge movement of the articular heads in the lower floor of the joint, the cartilaginous disc together with the head of the articular process slides forward, shifting to the articular tubercle. The condylar process of the lower jaw moves forward by approximately 12 mm. In the third phase (maximum lowering of the jaw), movement occurs only in the lower floor of the joint around the frontal axis. At this time, the articular disc is located on the articular tubercle. The mechanism of raising the lower jaw repeats the stages of its lowering in reverse order.
When the lower jaw is displaced forward, movement occurs only in the upper floor of the joint. The articular processes, together with the articular discs, slide forward and exit onto the articular tubercle in both the right and left temporomandibular joints.
With lateral displacement of the lower jaw, the movements in the right and left temporomandibular joints are not the same: when the lower jaw moves to the right, the articular head together with the disc slides forward in the left temporomandibular joint and comes out on the articular tubercle. Sliding occurs only in the upper floor of the joint. At the same time, in the joint on the right side, the articular head shifts around the vertical axis passing through the neck of the condylar process. When the lower jaw moves to the left, the head slides forward together with the articular disc in the right joint, and rotates around the vertical axis in the left.
On the X-ray of the temporomandibular joint in the lateral projection (with the mouth closed), the mandibular fossa of the temporal bone is visible as a depression. The articular tubercle protrudes forward. The head of the lower jaw has the shape of a semi-oval with smooth outlines. Between the head of the lower jaw and the mandibular fossa, an X-ray articular space is visible, wider in the middle than at the edges. With the lower jaw lowered, the head of the lower jaw is on the articular tubercle, and the mandibular fossa remains free.
What tests are needed?