TMJ Anatomy and How it Relates to TMJ Dysfunction (TMD)
What is TMJ?
The term TMJ is an abbreviation for two of the facial joints known as the Tempormandibular Joints. TMJ Dysfunction is any of the pathologies of the face that are associated with the two TMJs.
So we can fully understand the causes and the pathology associated with TMJ Dysfunction, we can look at the anatomy of the TMJ itself.
Here, we'll look at the anatomy of TMJ dysfunction using the help of a few pictures:
In a normal and healthy joint, the disc is concave on the top and bottom, and it acts as a lubricated protective barrier between the head of the mandible or jaw joint (condyle) and the joint space, also known as the fossa. The TMJ is encapsuled by this disc and in normal cases, there is no movement or vibrations that are associated when the mouth opens and closes.
When you open your jaw, the disc should stay in place and the head of the mandible (condyle) first rotates, then translates (moves forward and down) with help of the lateral pterygoid muscle. If there is TMJ dysfunction present, the disc sits in a number of places other than snug in between the condyle and fossa.
In some cases the posterior ligament gets over-stretched and the disc sits in front of the joint head. When this happens, the an anterior disc displacement occurs, which can be a major cause of TMJ dysfunction.
TMJ with anterior disc displacement - has TMJ dysfunction
Note how the retrodiscal tissues are stretched out and the bi-concave shape of the disc is anteriorly displaced. TMJ dysfunction occurs because when you open the jaw, the displaced disc "clicks" or "pops" back in place. Sometimes the click or pop is audible and can be heard, but at early stages or "partial disc displacement," the disc is not fully off of the condyle and often times there is no pain or uncomfortable feeling.
Depending on the trauma and the level of TMJ Dysfunction, the disc can be anteriorly displaced (in front), or it can be displaced to the side (medial or inside; lateral or outside).
What is TMJ?
Since TMJ is "Temporomandibular Joint, everybody has TMJ! In fact, they have two. So, when someone says, "I think I may have TMJ." What they really mean is, "I think I may have TMJ Dysfunction." This is often confused by the general public and when you go see a professional, you will often hear the clinician call it TMD for TMJ dysfunction. It is imporant to properly refer to the pathology because simply calling it TMJ just refers to the body part, similar to saying "I have nose" or "I have ear."
Generally speaking, dentists are the most knowledgeable professionals to treat the TMJ and TMD. However, not all dentists know about the TMJ.
Hope this helps -