Anatomy & Dysfunction of the TMJ

The TMJ or temporomandibular (jaw) joint is an incredibly hard working and complex synovial joint, that allows you to talk, eat, yawn, form facial expressions and also supports breathing. It is the only joint in the body that works bilaterally, which means that both sides of the joint work together to create movement. The TMJ is a ginglymoarthrodial joint, which means it moves as both a hinge and sliding joint, allowing for a wider variety of movement. The teeth limit the range of movement of the joint, but the actual resting position of the TMJ is with a small gap of a few mm between the teeth.

The TMJ is formed between the temporal bone and the mandible, the latter of which is the only moveable part of the skull. The ear canal sits directly behind the TMJ, which is significant in the symptoms that can result from TMJ dysfunction. The mandible has a structure called a ramus on each side. Each ramus has a condylar and coronoid process, and it is the condylar process that articulates with the temporal bone to form the TMJ. Between the temporal bone and the condylar process is an articular disc, which is a tough piece of connective tissue that is primarily composed of fibrocartilage.

The articular disc divides the joint making a synovial cavity above and below it, which have their own individual synovial membranes. The disc and synovial cavities all sit within a relatively loose joint capsule. The capsule contains retrodiscal tissue which fills some of the space in the posterior aspect of the capsule, and has a large supply of blood vessels and nerves, which makes it a big contender in the cause of TMJ dysfunction and pain.

Ligaments

Three main ligaments are associated with the TMJ – the temporomandibular ligaments, stylomandibular ligament and sphenomandibular ligament; all of which provide passive support. There are also two oto-mandibular ligaments that connect from the malleus (in the inner ear), called the discomalleolar ligament and the anterior malleolar ligament. The discomalleolar ligament connects from the malleus to the retrodiscal tissue, while the anterior malleolar ligament connects from the malleus to the mandible via the sphenomandibular joint. These two ligaments are possibly what gives rise to tinnitus in some circumstances, and can quite commonly be associated with TMJ dysfunction.

Muscles

Masseter: This muscle is composed of 3 layers, which attaches across the jaw and helps us to chew by elevating (closing) the jaw and aiding the mandible in an outward protrusion movement. It was only recently discovered that the masseter is actually made up of 3 layers, whereas it was previously thought of to only have 2 (superficial and deep layers). The 3rd layer is the deepest layer, and has it’s own unique additional function in helping the jaw to retract, which is when it moves back towards the ears.

Lateral Pterygoid: This is a muscle with two heads, which attach between the sphenoid bone of the skull and the jaw. One head attaches to the TMJ joint capsule, while the other attaches to the mandible. This muscle also allows for protrusion movements of the jaw, but also aids depression (opening) of the jaw. It can also aid with rotation movements.

Medial Pterygoid: This muscle does the same role as the lateral pterygoid, however it attaches in a different place. It attaches to the maxilla, palatine and sphenoid of the skull, as well as the mandible.

Temporalis: As the name suggests this muscle attaches to the temporal bone of the skull, and then it also attaches to the mandible. It’s the largest of the TMJ muscles, and it can often be the muscle that is responsible for headaches and migraines, that can be triggered by TMJ dysfunction. It’s function is to elevate and retract the mandible.

Dysfunction

A number of symptoms can occur when there is dysfunction in the TMJ or surrounding muscles/fascia. The 3 finger test can determine potential myofascial restrictions that are causing or contributing to TMJ dysfunction. This is a really quick and easy test. Place 3 fingers vertically between your front top and bottom teeth. If you cannot open your mouth wide enough for 3 fingers to fit comfortably, then it is likely that there are restrictions affecting the joint function. However, some people with restrictions and dysfunction in their TMJ can still perform the 3 finger test successfully, so alone it only provides some of the picture.

The symptoms of myofascial TMJ dysfunction include:

  • Jaw pain
  • Neck or shoulder pain
  • Headaches or sinus pain
  • Ringing in the ears (tinnitus)
  • Problems when swallowing
  • Teeth grinding (bruxism)
  • Clicking or popping in the joint
  • Toothache
  • Limited range of motion

Treatment

Myofascial TMJ dysfunction treatment is for tight muscles and fascia surrounding the TMJ, and involves a number of techniques including soft tissue release, myofascial release and instrument assisted mobilisation of the head, face, neck and shoulders. Treatments include both intra-oral (inside mouth) as well as external treatment. Often the treatment can also include the hips, glutes and abdominals due to the fascial connection between the hips and jaw (I will be writing an article on this interesting connection soon).

References

“Mandible jaw bone labeled anatomical structure scheme vector illustration” Vector Mine Via: https://vectormine.com/item/mandible-jaw-bone-labeled-anatomical-structure-scheme-vector-illustration/

“The Temporomandibular Joint” Ken Hub Via: https://www.kenhub.com/en/library/anatomy/the-temporomandibular-joint

“TMJ Anatomy” Physiopedia Via: https://www.physio-pedia.com/TMJ_Anatomy

“The mysterious connection between your pelvis and jaw” Align PT Via: https://www.alignpt.com/mysterious-connection-pelvis-jaw/

Images Sourced From: https://pocketdentistry.com/29-temporomandibular-joint/, https://museumdental.com/jaw-clicking-popping-explained/,

Please note that Anatomy Overload does not take responsibility for the content of third party links provided in the references.

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