The temporomandibular joint the tmj is the joint between the lower jawbone the mandible and the temporal bone of the skull. The TMJ is responsible for jaw movement and is the most used joint in the body. The TMJ is essentially the articulation between the condyle of the mandible and the mandibular fossa a socket in the temporal bone. The unique feature of the TMJ is the articular disc a flexible and elastic cartilage that serves as a cushion between the two bone surfaces. The disc lacks nerve endings and blood vessels.
In its center and therefore is insensitive to pain. anteriorly it attaches to lateral pterygoid muscle a muscle of chewing. Posteriorly it continues as retrodiscal tissue fully supplied with blood vessels and nerves. The mandible is the only bone that moves when the mouth opens. The first 20 mm opening involves only a rotational movement of the condyle within the socket. For the mouth to open wider, the condyle and the disc have to move out of the socket, forward and down the articular eminence, a convex bone surface located anteriorly.
To the socket . this movement is called translation. The most common disorder of the TMJ is disc displacement, and in most of the cases, the disc is dislocated anteriorly. As the disc moves forward, the retrodiscal tissue is pulled in between the two bones. This can be very painful as this tissue is fully vascular and innervated, unlike the disc. The forward dislocated disc forms an obstacle.
For the condyle movement when the mouth is opening. in order to fully open the jaw, the condyle has to jump over the back end of the disc and onto its center. This produces a clicking or popping sound. Upon closing, the condyle slides back out of the disc hence another click or pop. This condition is called disc displacement with reduction . In later stage of disc dislocation, the condyle stays behind the disc all the time, unable to get back onto the disc, the clicking sound disappeared but mouth opening is limited.
This is usually the most symptomatic stage the jaw is said to be locked as it is unable to open wide. At this stage the condition is called disc displacement without reduction Fortunately, in majority of the cases, the condition resolves by itself after some time. This is thanks to a process called natural adaptation of the retrodiscal tissue, which after a while becomes scar tissue and can functionally replace the disc. In fact, it becomes so similar to the disc that it is called a pseudodisc.
Diagnosis and Treatment of TMJ Disorders
Welcome to the stanford health library. Thank you for coming here tonight. My name is Michele Jehenson and I work at the orofacial pain at the Stanford Pain Center in Redwood City. So today’s topic is TMJ disorders. TMD, I’m going to speak about the nature of the disorder.
What a tmj disorder really is. I’m going to also talk about who is at risk for TMD. And finally, I will touch on the common treatments that are recognized as evidencebased treatment for TMJ disorders. So, I guess it’s customary to.
Talk about disclosures as to if i’m affiliated with any kind of pharmaceutical company or anything like that. I have no disclosures to be done. So, I wanted to first show you the anatomy of a TMJ. It’s a joint that is very unique in the body. It’s one of a kind.
There is a one disc, and you can picture it as a donut. So, it’s a circular, biconcave, just a donut, just doesn’t have the actual hole in the middle. So it’s kind of like a donut shape, and it separates the jawbone, which you see as the rounded bone in the picture, from the skull.
And particularly, the fossa, the articular fossa, and the eminence that you see to the right of the fossa. So the disc is flexible. It’s fiber cartilage, and it offers a perfect interface between the skull and the jaw. It allows for smoother motion.
The joint is also particular in a sense that not only it allows rotation of the joint, but it allows for forward motion of the jaw. So, if you put your hand like slightly over your, in front of your ear and you open your jaw wide and slow, you can see that initially, it just starts rotating and.
Then you can feel it actually advance forward. And for some people, you can actually feel it coming out slightly, because even though the jaw is seemingly fixed, the suture that is in the front, it allows for certain flexibility in and out of the joint itself. So, what is a TMJ disorder?.
So, a tmj disorder is defined by pain, either at rest or upon function. It is defined by something that is a painful noise. It can also be just a dysfunction, like a limited range of motion, or a jaw deviation such as this, like when you open you go to one side or.