TMJ Anatomy

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Description

The temporomandibular joint (TMJ) is the joint between condylar head of the mandible and mandibular fossa of the temporal bone.  It is a condylar and hinge-type joint that has thousands of repetitive movements daily.  The joint involves fibrocartilaginous surfaces and a disc which divides the joint into two cavities. 

Motions Available

Mandibular depression and elevation, right and left lateral excursion/deviation, and protrusion and retrusion. 

Ligaments & Joint Capsule

The articular disc of the TMJ is divided into anterior, intermediate, and posterior zones and is thinnest in its intermediate zone and thickest in its posterior zone helping maintain disc positioning on the condyle. The disc is firmly attached at the medial and lateral poles by the collateral or discal ligaments, to the highly vascular and innervated retrodiscal tissue posteriorly, and to the joint capsule and the superior lateral pterygoid muscle anteriorly. The capsule and extracapsular ligaments help stabilize the TMJ. 

Muscles

Muscles of Mastication:

Temporalis: superior attachment to temporal bone and inferior attachments to coronoid process and anterior ramus of mandible, involved with elevation and retrusion, ipsilateral lateral excursion and clenching

Masseter: fibers run obliquely from zygomatic arch to the angle of the mandible, involved in ipsilateral lateral excursion and clenching

Medial pterygoid: fibers attach at the pterygoid fossa to the medial aspect of the angle of the mandible, involved in elevation and protrusion and unilaterally in contralateral excursion.  Also involved in grinding.

Superior lateral pterygoid: attaches at sphenoid and neck of the condyle, anterior capsule, and disc.  Fires in conjuction with mandibular elevators, plays a role in positioning the disc at end range closure and with resistance closure with chewing.

Inferior lateral pterygoid: attaches to the lateral pterygoid plate and the neck of the condyle.  Involved in gliding the condyle anteriorly during mouth opening and during protrusion.  Unilaterally involved in contralateral excursion. 

Closed Packed Position

Teeth tightly clenched

Open Packed Position

Resting position: mouth slightly open, lips together, teeth not in contact, tongue on hard palate.

Resources

Recent Related Research (from Pubmed)

References

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