TMJ Anatomy
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Description[edit | edit source]
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. [1]
Motions Available[edit | edit source]
Mandibular depression and elevation, right and left lateral excursion/deviation, and protrusion and retrusion.
Ligaments & Joint Capsule
[edit | edit source]
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. [2]
Muscles[edit | edit source]
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. [3]
Closed Packed Position[edit | edit source]
Teeth tightly clenched
Open Packed Position[edit | edit source]
Resting position: mouth slightly open, lips together, teeth not in contact, tongue on hard palate.
Other Important Information[edit | edit source]
During opening of the TMJ, the hinging motion predominates for the first 20 mm of motion and is primarily due to gravity. Then anterior translation and rotation of the condyle makes the superior lateral pterygoid relax as the condyle approaches the intermediate zone of the disc. As this occurs the shape of the disc along with the attachment of the collateral ligaments results in anterior translation of the disc. The inferior lateral pterygoids contract, resulting in continue anterior translation. At full opening, the condyle resides in a slightly anterior position on the disc, the disc and condyle rest on the articular eminence of the temporal bone, the superior lateral pterygoid is on slack, and the retrodiscal tissue is stretched.
Normal movements: Normal opening is approximately 35-40 mm or 2-3 finger between upper and lower incisors, protrusion is 3-7 mm, lateral deviation is 5-12 mm. [4]
Resources[edit | edit source]
Recent Related Research (from Pubmed)[edit | edit source]
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References[edit | edit source]
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- ↑ Magee D. Orthopedic physical assessment. 4th ed Philadelphia: Saunders. 2002.
- ↑ Harrison AL, The temporomandibular joint. In: Malone TR, McPoil T, Nitz AJ editors. Orthopedic and sports physical therapy. St Louis: Mosby, 1997. p555-93.
- ↑ Harrison AL, The temporomandibular joint. In: Malone TR, McPoil T, Nitz AJ editors. Orthopedic and sports physical therapy. St Louis: Mosby, 1997. p555-93.
- ↑ Clarkson HM. Musculoskeletal assessment: joint range of motion and manual muscle strength. 2nd ed. Philadelphia: Lippincott Williams and Wilkins. 2000.
