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.
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Acrylic models of a normal TMJ. When the mouth is closed, the articular disc is in its normal position; when opening, the disc follows the anterior movement of the condylar head |
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.
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Disc displacement with reduction. The disc is dislocated anteriorly when the mouth is closed and slides back onto the condyle as the mouth opens |
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.
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Disc displacement without reduction. The disc is totally displaced in the closed mouth position and does not slide back to the condyle when opening |
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.
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Broad adhesion within the upper joint compartment with signs of severe inflammation. The adhesion is cut with micro scissors under direct arthroscopic vision |
