The new diagnostic criteria for TMJ developed by the international working group, the RDC-TMD Consortium, which has been embraced by the American Dental Association (ADA) does a lot for standardizing diagnosis of TMJ, including the diagnosis of four types of disc displacement, which may be unfamiliar to people who have not yet been diagnosed with TMJ. However, these types of disc displacement and other joint problems have a large influence on the type of symptoms you have with your TMJ, although symptoms don’t always correspond to the physical position of your jaw.

What Is Disc Displacement?

The temporomandibular joint is where the jaw meets the skull. Between the two bones there is, as there is at all joints, a cushioning disc of cartilage. Ideally, this disc should stay in place to prevent the bones from rubbing against each other and causing pain and damage. But in many cases of TMJ, the disc has become displaced.

This is also sometimes called internal derangement.

Disc Displacement with Reduction

The first stage in TMJ is typically disc displacement with reduction. In this disorder, the disc is displaced forward of where it’s supposed to be, but it still performs some functional role as cushion. As you open your jaw, the pressure rests on the disc, compressing or reducing it. However, you likely experience popping or clicking as a result of the disc movements.

There are two types of disc displacement with reduction: with and without locking. Both have clicking, but in the with locking condition, the disc sometimes slips into a position where it doesn’t reduce during opening, which can lead to interference with your mouth opening. You may be able to overcome this by maneuvering your jaw in a slightly different way.

Disc Displacement without Reduction

In this condition, the cushioning disc has moved so far out of position that it isn’t cushioning the joint anymore. Therefore, it doesn’t get compressed, i.e. reduced. This can occur with either locking of the jaw or without locking. When locking occurs in disc displacement without reduction, you can’t maneuver your jaw in such a way as to open your jaw.

Degenerative Joint Disease

In degenerative joint disease, your joint disc and other tissues have degraded. This can follow on from disc displacement or it can be independent of disc displacement. Once the joint disc is degenerated, the bones begin to wear. You may hear any kind of joint noise, but the most worrisome is crepitus, a grinding sound made by bones scraping against one another.


In this disorder, your jaw has essentially popped out of place, including both the disc and the condyle–the round, bony part of the jaw that fits into the joint. When this occurs, your jaw will seem to stick open, but you can maneuver it in such a way that it will close again. It can progress to luxation, in which you are unable to maneuver your mouth to close it.

What Is the Problem with Your Jaw?

If you are experiencing jaw sounds and jaw pain, a proper diagnosis can lead us to the right treatment to relieve your symptoms. To learn what is the condition of your jaw, please call (803) 781-9090 today for an appointment with a TMJ dentist in Columbia, SC at Smile Columbia Dentistry.