How to diagnose a jaw dislocation

Does your patient have a dislocated jaw? Learn how to diagnose a temporomandibular (TMJ) dislocation here.
Last update19th Nov 2020

The correct medical term for a jaw dislocation is a temporomandibular joint (TMJ) dislocation. TMJ dislocation happens when the mandibular condyle dislocates forward on one or both sides of the jaw.

How does a jaw dislocation happen?

While dislocation can result from trauma, most of the time it happens when a patient has an extreme mouth opening, such as a huge yawn!

Figure 1. Anatomy of the temporomandibular joint (TMJ).

How to diagnose a jaw dislocation

Physical signs of a jaw dislocation

Like other dislocations, muscle spasms will prevent the jaw from reducing. In the case of a TMJ dislocation, the masseter muscle is the culprit. This muscle connects the mandible (lower jaw) to the maxilla (upper jaw) and helps you chew.

Usually, a dislocated jaw is obvious! There are three signs to look for when diagnosing a jaw dislocation:

  1. The patient’s mouth is open.
  2. The patient cannot close their mouth.
  3. The patient cannot speak properly.
Figure 2. A patient who has dislocated their jaw exhibits three typical signs: the patient’s mouth is open, and the patient cannot close their mouth, or speak properly.

Patients who have dislocated their jaw previously are more likely to repeat it. Unless the patient has had a previous dislocation, they are generally very anxious. However, the pain is variable across patients.

Diagnostic tests for a jaw dislocation

You can confirm the diagnosis with a mandible x-ray or computed tomography (CT) scan. Usually, the main reason for imaging is to confirm that there is no fracture in the setting of trauma.

Figure 3. Physical tests for a jaw dislocation. Confirm the jaw dislocation with a mandible x-ray or computed tomography (CT) scan.

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That’s it for now. If you want to improve your understanding of key concepts in medicine, and improve your clinical skills, make sure to register for a free trial account, which will give you access to free videos and downloads. We’ll help you make the right decisions for yourself and your patients.

Recommended reading

  • Roberts, J. 2019. “Management of common dislocations”. In: Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care. 7th edition. Philadelphia: Elsevier.  
  • Roberts, J. 2019. “Otolaryngologic procedures”. In: Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care. 7th edition. Philadelphia: Elsevier.  

About the author

Siamak Moayedi, MD
Associate Professor and Director of Medical Student Education, University of Maryland and Course Director, Essential and Critical Procedures, Emergency Medicine.