The temporomandibular (TM) joints are located just anterior to the opening of each ear. These bilateral synovial joints hinge and slide on their fibrocartilaginous surfaces to provide movements of the mandible. These movements occur in most people without any problem, which is remarkable considering the incongruent and naturally unstable design.
If the joint remains functional and non-painful, then chewing, talking and displaying a wide range of facial expressions goes on practically unnoticed by the person. However, once temporomandibular dysfunction (TMD) develops, life is anything but normal. Symptoms of TMD include headache in a variety of patterns, toothache, burning or tingling sensations in the face, tenderness and swelling on the sides of the face, clicking or popping of the joint, reduced range of motion, ear pain without infection, hearing changes, dizziness, sinus-type responses, overt pain behaviors and postural changes. It is characterized by so many symptoms that could arise from other ailments that it has a strong reputation as an elusive, baffling condition.
“Temporo” refers to the temporal bones which make up the side of your skull. “Mandibular” refers to the mandible or lower jaw. Temporomandibular joint is where those two bones come together. A viscous synovial fluid provides a liquid environment with a small pH range that lubricates and nourishes the disc as well as the joint surfaces, thereby reducing the possibility of friction and erosion.
Although all functions of the articular disc are not completely understood, its design displays the ability to remodel in response to stress, changing shape to accommodate imposed forces, such as the mechanics of chewing, grinding and talking, or from chronic head positioning and other postural compensations. It also provides shock absorption, improvement of fit between surfaces (congruity), facilitation of combined movements (slide and rotation), checking of translation, deployment of weight over larger surfaces, protection of articular margins, facilitation of rolling movements and the spread of lubrication. Whew! That sure is a lot going on in such a small space!
It is often suggested that the discs stabilize the temporomandibular joint while allowing considerable movement of roll, spin and glide of the condylar head. These movements are often performed with full loading while also attempting to reduce the possibility of trauma. Does this create stability? Gray’s anatomy (2005) implies otherwise, suggesting “its function is to destabilize the condyle (certainly not to stabilize it) in the same way that stepping on a banana skin destabilizes the foot.” This concept certainly makes more sense given the slippery, sloped surface on which the disc travels.
Conditions that improve the chances for healthy TM joint function include:
* both discs being firmly attached to their respective condyles
* each disc resting in ideal position to load and transport the mandible
* internal joint surfaces being well nourished and lubricated by healthy synovia
* normal range of joint motions
* symmetrical postural balance
* masticatory muscles being free of contractures
* no significant traumas having been suffered by the joint
Real-life situations seldom offer all of these conditions simultaneously. More often, various combinations to the contrary are observed and with nutritional, emotional and structural stresses imposed as well. Although historically TMD has been thought to be primarily based on mechanical dysfunction (such as disc derangement, malocclusion, deformity or bruxism) and has been primarily addressed by the dental profession, a more integrated biopsychological model has now emerged. A whole team of clinicians, each influencing the body and its healing process while interfacing with each other, is often required to achieve long-term results. Understanding the role that you play, as well as those of other team members, is an important step in the success of the treatment plan.
DeLany J 1997 Temporomandibular dysfunction. Journal of Bodywork and Movement Therapies 1(4):198–202
Gray’s anatomy 2005 (Standring S, ed) 39th edn. Churchill Livingstone, Edinburgh