Question: What causes the jaw to lock and what should I do?
Explanation: A locked jaw may be locked closed, unable to open, or locked open, unable to close. Locking closed, called trismus, commonly results from infection, muscle spasm, or a displaced temporomandibular joint disc that blocks translation. Locking open usually reflects condylar dislocation, often after a wide yawn or a long dental appointment. Trismus alongside fever, swelling, or difficulty swallowing suggests spreading infection and is a red flag. A dislocated jaw requires reduction by a trained clinician. Do not force the jaw yourself.
Related Questions:
What is trismus?
Restricted mouth opening, conventionally defined as less than about 35 millimetres between the incisal edges. Causes include infection, muscle spasm, joint pathology, and, rarely, tetanus. Trismus accompanying facial swelling and fever indicates spreading dental infection and requires urgent assessment.
My jaw is stuck open, what should I do?
Do not force it. Attend an emergency department or a dentist experienced in reduction. The condyle has usually slipped forward past the articular eminence and requires a specific manipulation, sometimes with sedation or muscle relaxants. The longer it stays dislocated, the harder reduction becomes.
Can jaw locking be caused by teeth grinding?
Indirectly. Chronic grinding fatigues and shortens the masticatory muscles and loads the joint, contributing to disc displacement. A disc that displaces without reduction blocks opening. Night guards, jaw exercises, and physiotherapy form the mainstay of conservative management.
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