Lockjaw or trismus refers to any condition with reduced ability to open the mouth. A person with lockjaw temporarily (in some cases, permanently) loses the ability to open and/or close the mouth. Some cases of lock jaw can cause extreme pain and discomfort. When left untreated, lock jaw can permanently impair the motor functions of the jaw, particularly when it comes to chewing or talking. The jaw joints play an important role in jaw movements. These are points of attachment of the lower jaw to the skull, one on each side of the face, just in front of the ears. Ligaments, tendons and muscles support the joint and are responsible for the various jaw movement. Jaw movement will be affected if any of these get injured.


Lock jaw can be caused by a number of factors:-

  • Tetanus infections are common causes of lockjaw. Tetanus causes prolonged contraction of the skeletal muscle fibers and can lead to painful and violent spasms. One of the first signs of tetanus infections is lockjaw.
  • Jaw dislocation – This happens when jaw joint moves too far forward and gets stuck in front of bony prominence. The surrounding muscle often goes into spasm and hold the jaw joint in a dislocated position.
  • Inflammation of muscles and soft tissues around the jaws is the leading cause of lockjaw. Impacted wisdom tooth can cause the soft tissue surrounding the tooth to get inflammed. Infection originating from the lower back teeth can also cause inflammation of the surrounding tissue and abscess formation (accumulation of pus). This will lead to impaired function of the muscle that opens the jaw (muscle spasm)
  • Limitations caused by factors internal to the joint include bony ankylosis (bone growth within the joint), fibrous ankylosis, arthritis, infections and trauma
  • Side effects of some medications, particularly those used for psychiatric and mental disorders.
  • Iatrogenic causes e.g. complication of dental injection (when local anaesthetic is accidentally injected into the jaw muscle) and post-wisdom tooth extraction (in which the muscles of mastication may be torn, or the joint become hyperextended)

Sign and symptom

These include:-

  • Difficulty in opening the mouth
  • Intermittent ‘locking’ episodes
  • Reduced amount of mouth opening
  • Difficulty in chewing and swallowing
  • Change in the speech pattern
  • Pain in the joints associated with jaw movement


There are a number of complications if the problem is not treated. These are:-

Difficulty with eating.

  • This will result in inadequate nutrition. Only a very small amount of food can be taken at one time.The patient may experience significant weight loss, and may have significant nutritional deficits
  • Limited mouth opening may make proper mastication of food more difficult (problem with swallowing)

Poor oral hygiene

  • Limited mouth opening can result in compromised oral hygiene. This can result in dental caries and gum diseases  which can lead to infection.

Joint immobilization

  • When a joint is immobilized, degenerative changes occur within the joint. These may result in inflammation, pain and fusion of the joint ( ankylosis )

Treatment – Depends on the cause of the lockjaw.

The types of treatment available for lockjaw are : –

Warm compress

  • For mild to moderate cases of lock jaw, a warm compress can reduce the stress and pain


  • Lock jaw caused by an infection from an impacted wisdom tooth can be eliminated and corrected by  removal of the tooth
  • Lock jaw caused by fusion of the joints can be corrected by surgery
  • Dislocation of jaw can be corrected by manual reduction. Chronic cases may need surgery.

Muscle relaxant

  • Controlled doses of muscle relaxants can overcome the tensed-up muscles in the jaw that remain contracted even if they’re not being used


  • Lockjaw caused by infection or inflammation ( such as tetanus or infection from the tooth ) can be treated with antibiotic and anti-inflammatory drugs


Prevention of lock jaw

  • Tetanus vaccination
    • The primary symptom of tetanus is lockjaw. Vaccination minimizes the risk of contracting tetanus
  • Avoid side effects of some medications, especially for psychiatric illnesses and mental disorders. Always check the drug insert if an immobile jaw is part of the side effects of the medication.
  • Regular dental check up to prevent unnecessary infections originating from teeth.


  • Dental rehabilitation
    • Assessment of the dental occlusion will minimize trauma to the jaw joint
  • Physiotherapy rehabilitation
    • Rehabilitating the muscles of the jaw  to their normal function
    • Rehabilitating the mobility of the  jaw joints


  1. Malaysian Association of Oral and Maxillofacial Surgeon.
  2. Malaysian Dental Council.
  3. Malaysian Dental Association.
Last reviewed : 20 April 2012
Writer : Dr. Marzuki b. Zainal Abidin
Accreditor : Dr. Kok Tuck Choon