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Problems in the structure of the jaw joint include:

• Problems in the bones or other structures of the joint. These may have been present since birth (congenital), developed over time, or been caused by injury.
• Problems with the disc that cushions the joint between the jawbone (mandible) and the skull, such as the disc moving out of its normal position (disc displacement) or tearing (usually the result of a long-standing joint dysfunction).
• Arthritis, which can cause wearing away of the disc or inflammation of the membranes lining the joint (synovitis).
• Scar tissue within the joint (adhesions).
• In rare cases, tumors in or near the jaw joint.

Injury to the temporomandibular (TM) joint most commonly occurs when too much stress is placed on the joint by:

• Chewing hard or chewy foods.
• Bruxism (grinding or clenching the teeth) over a period of time, and especially during sleep.
• Dental procedures that require the jaw to be held open too wide for a long time.

These stressors can cause the articular disc to shift out of its normal position (disc displacement). Because this disc cushions the joint between the jawbone (mandible) and the skull, displacement can result in pain and locking of the joint.

A blow to the jaw, TM joint dislocation, or jaw fracture can also result in TM disorder symptoms.