TMJ Anatomy

The TJM is defined as a gingival joint [2] because it has rotational motion in the sagittal plane and translational motion on its own axis – this translational motion creates more motion. [3] These movements are constrained by various passive factors as well as passive tension. Ligaments and muscles. [4]

TMJ dysfunction can lead to severe pain and lifestyle restrictions.

Temporomandibular joint disorders are common, and patients often seek physiotherapy advice and treatment.

A good understanding of the anatomy of the TMJ and associated structures is essential for proper diagnosis and appropriate treatment.

Joint

The TMJ is a synovial condyle and hinge type joint. The joint involves a fibrocartilaginous surface and an articular disc that divides the joint into two cavities. [5] These superior and inferior articular cavities are lined with separate superior and synovial membranes [6].

Joint capsule – The joint capsule is a fibrous membrane that surrounds the joint and attaches to the articular process, articular disc, and neck of the mandibular condyle.

Articular disc – The articular disc is the fibrous extension of the joint capsule that runs between the two articular surfaces of the temporomandibular joint. The intervertebral discs articulate with the mandibular fossa of the temporal bone above and the condyle joints of the mandible below. The disc divides the joint into two parts Each part has its own synovium. The discs are also attached medially and laterally to the condyles by collateral ligaments. The anterior disc attaches to the joint capsule and the superior head of the lateral pterygoid. The posterior part is attached to the mandibular fossa and is Known as the retrodiscal tissue [7].

Retrodiscal tissue – Unlike the disc itself, the retrodiscal tissue is vascular and highly innervated. Thus, retrodiscal tissue is often the primary cause of pain in temporomandibular disorders (TMD), especially when there is inflammation or compression within the joint [8]

Ligaments

Ligaments provide passive stability to the TMJ.

The temporomandibular ligament is the thickened part of the outer joint capsule, which is divided into two parts: the external oblique part and the internal horizontal part.

The stemmandibular ligament extends from the styloid process to the angle of the mandible. The sphenomandibular ligament arises from the sphenoid spine and inserts on the mandibular tongue.

The auriculomandibular ligament is the intermallear ligament (DML) that originates from the malleus (a small bone in the middle ear) and extends to the medial retrodiscal tissue of the TMJ and the anterior malleolus ligament (AML) that originates from the malleus and connects to the The mandible passes through the sphenomandibular ligament [9][10]. The auromandibular ligament may be involved in TMD-related tinnitus. A positive correlation between tinnitus and ipsilateral temporomandibular joint disturbances has been found [11][12]. It has been suggested that TMJ disorders may stretch DML and AML Thus affecting the structural balance of the middle ear [13][14][15][16]. “Therefore, ear symptoms (tinnitus, otalgia (ear pain), dizziness, and hearing loss) that appear to correspond to altered spatial relationships of the ossicles (such as conductive middle ear lesions) can also be caused by Lesions of the masticatory system. “[17]

Movements

Various movements occur at the TMJ. These movements are mandibular depression elevation lateralization (occurring on the right and left side) retraction and protrusion.

Each of these movements is accomplished by a number of muscles that work together to perform the movement while controlling the position of the condyle within the mandibular fossa.

Chewing and speaking require a combination of jaw movements in multiple directions [18][19].

[20]

Muscles

For a more detailed description, see the Masticatory Muscles page.

Muscle action Temporal muscle elevates mandible Masseter elevates mandibular lateral pterygoid Rear extension Mandible depresses lateral mandibular deflection Medial pterygoid elevates mandible with masseter auxiliary protrusion bone mandible resistance resistance The platysma depresses the mandible against resistance while the infrahyoid stabilizes or depresses the hyoid

Adapted from Moore[6]

static position and close-packed position

The resting position of the TMJ is with the mouth slightly open, the lips together, and the teeth not touching. This is in contrast to the closed position of the teeth clenched. [5]

Nerve Supply

Muscles acting on the TMJ are innervated by the mandibular nerve (CN V) and the facial nerve (CN VII) C 1 C 2 and C 3. [6]