The articular disc provides a cushion between the ball and socket of the temporomandibular (TM) joint. It is very common for the TM joint to painlessly click or pop while opening or closing. These sounds are related to the ball (condyle) of the joint passing over the disc as the jaw opens or closes. Such painless noises are not a cause for concern.

As a result of joint stress or injury to the jaw joint, the disc and its band of connective tissue can become stretched out, allowing the disc to shift out of its normal position (disc displacement). As the joint moves, the disc can:

• Become stuck in front of the condyle, locking the jaw.
• Fold over itself. Sometimes, the condyle then presses on soft tissue that is normally protected by the disc, causing pain and swelling.

Often treatment of a displaced disc will also help relieve the accompanying muscle tension or spasm. Splint therapy temporarily creates space between the TM joint's ball and socket, allowing the disc to gradually return to its original position.

Surgery is rarely appropriate but may be used in severe cases involving disc tearing or chronically disabling disc displacement.

The pain and dysfunction related to a displaced or damaged disc are common temporomandibular (TM) disorder symptoms. However, not all TM disorders involve disc displacement; some are exclusively muscle-related.