Editing Temporomandibular joint

{{Infobox anatomy
| Name         = Temporomandibular joint
| Latin        = Articulatio temporomandibularis
| Image        = 
| Caption      = Lateral view of the TMJ showing the articular disc, condyle, and mandibular fossa.
| System       = [[Skeletal system]], [[Muscular system]]
| Articulation = [[Condylar process]] of the [[mandible]], [[Mandibular fossa]] of the [[temporal bone]]
| Nerve        = [[Auriculotemporal nerve]], [[Masseteric nerve]]
}}

==Definition==
The '''temporomandibular joint (TMJ)''' is the bilateral [[synovial joint]] that articulates the [[mandible]] (lower jaw) to the [[temporal bone]] of the [[skull]]. It is unique in the human body as a '''ginglymoarthrodial joint''', meaning it allows for both hinging (rotation) and gliding (translation) movements.

The two joints must function in unison to facilitate [[mastication]], speech, and yawning.

==Anatomy and Structure==

===1. Articular Surfaces===
* '''Mandibular Condyle''': The superior-posterior part of the mandibular ramus.
* '''Mandibular Fossa''' (Glenoid Fossa): The depression in the temporal bone.
* '''Articular Eminence''': The raised bony projection anterior to the fossa that guides the condyle during translation.

===2. The Articular Disc (Meniscus)===
The TMJ is divided into upper and lower compartments by a biconcave '''articular disc''' made of dense [[fibrocartilage]] (unlike most synovial joints which use hyaline cartilage). 
* The disc is avascular and non-innervated in its central load-bearing zone.
* It is attached posteriorly to the '''retrodiscal tissue''' (bilaminar zone), which is highly vascular and innervated.

===3. Ligaments===
The joint is stabilized by several key ligaments:
* '''Temporomandibular (Lateral) ligament''': Prevents excessive posterior and lateral displacement.
* '''Sphenomandibular ligament''': An accessory ligament.
* '''Stylomandibular ligament''': Limits excessive protrusion of the mandible.

==Biomechanics and Movement==
TMJ movement occurs in two distinct phases:
# '''Rotation (Hinging)''': Occurs in the '''lower compartment''' (between the condyle and the disc) during the first 20–25 mm of mouth opening.
# '''Translation (Gliding)''': Occurs in the '''upper compartment''' (between the disc and the temporal bone) as the condyle moves forward down the articular eminence for wide opening.

==Clinical Significance==

===Temporomandibular Disorders (TMD)===
TMD is a broad term encompassing pain and dysfunction of the TMJ and the [[masticatory muscles]].
* '''Internal Derangement''': Most commonly '''[[Disc Displacement with Reduction]]''', characterized by a "click" or "pop" as the disc snaps back into position during opening.
* '''Disc Displacement without Reduction''': Often leads to "closed lock," where the patient has limited opening because the disc acts as an obstruction.

===Dislocation (Subluxation)===
Occurs when the condyle moves anteriorly past the articular eminence and becomes trapped, preventing the patient from closing their mouth.

===Bruxism===
Chronic grinding or clenching can lead to flattening of the condyle, perforation of the disc, or hypertrophy of the associated muscles (e.g., [[masseter muscle]]).

==See Also==
* [[Mandible]]
* [[Masticatory muscles]]
* [[Occlusion (dentistry)]]
* [[Orofacial pain]]

[[Category:Anatomy]]
[[Category:Oral Surgery]]
[[Category:Orthodontics]]