Pain and dysfunction in the temporomandibular joint are generally associated with displacement of the articular disc (which used to be called disc luxation). In a healthy temporomandibular joint, the disc sits on the condyle of the lower jaw when the mouth is closed.

Normal disc position

Magnetic resonance imaging (an MRI scan) clearly shows the position of the articular disc when the mouth is opened and closed. The following acrylic models of the temporomandibular joint show the position of the articular disc even more clearly. These models show the bony structures in white and the disc in red.

Disc displacement with reduction

If the disc slips forwards from its normal position this is referred to as disc displacement. The articular disc is initially only in front of the condyle of the lower jaw when the mouth is closed, but then as the mouth opens it slides back onto the condyle. This process is accompanied by a clearly audible click in the temporomandibular joint.

Disc displacement without reduction

Sometimes the temporomandibular joint clicks for months or even years before it suddenly jams. One day, the disc just does not slide back onto the mandibular condyle. It is difficult and painful to open the mouth; it can also be very difficult to chew. This is called a "closed lock". The temporomandibular joint does not click when this happens. This lock can last a very short time - for a split second - or longer, for minutes or hours.

Formation of adhesions

If it lasts longer, it is essential to seek advice from a temporomandibular joint specialist immediately. If this lock lasts for several days, it is very difficult, even for a specialist, to mobilise the disc again. The longer the disc displacement without reduction goes without being treatment, the greater the risk of adhesions forming in the joint, thereby permanently restricting mouth opening.