What Causes Lockjaw?

Medically Reviewed on 1/31/2022

7 Possible causes of lockjaw

Several nerves and muscles control jaw movement.
Several nerves and muscles control jaw movement.

Several nerves and muscles control jaw movement. Due to their anatomical arrangement, lockjaw is typically characterized by a partially open jaw position. The seven possible causes of lockjaw may include:

  1. Temporomandibular joint disorder (TMJ disorder): It is one of the prime reasons for lockjaw. TMJ disorders can develop due to arthritis, inflammatory disease, or facial accidents/injuries.
  2. Infections: Any infections around the oral cavity, such as tonsilitis, may sometimes affect the movement of the joint.
  3. Tetanus: This may occur due to a life-threatening neurotoxin that is released by Clostridium tetani. This is a bacterium commonly present in the environment. This toxin can cause TMJ muscle spasms. Tetanus is a huge risk factor for lockjaw. When lockjaw is a complication of tetanus, it can take weeks or even months for the condition to clear.
  4. Cancer: In some cases, carcinoma removal or radiotherapy can damage the jaw structure and restrict its movements.
  5. Sometimes, when chewing or yawning, the bite may be placing unnecessary pressure on facial, neck, and jaw muscles. When the top teeth don’t line up with the bottom teeth the way they are supposed to (malocclusion), nearby muscles can become irritated, inflamed, and tight. This makes them stiff and results in the locking sensation.
  6. In some situations, the jaw itself may also be causing the problem. The anatomy of the jaw includes the bone, muscles, and cartilage. The cartilage keeps the jawbone from rubbing against the skull. Sometimes this cartilage is damaged either because of an accident or as a result of clenching or grinding. Once damaged, it can slip over the bone, blocking the hinge joint from functioning.
  7. On rare occasions, side effects of some medications, particularly those used for psychiatric and mental disorders can also cause lockjaw.

What is a lockjaw?

Lockjaw or trismus refers to any condition with a reduced ability to open the mouth. A person with a lockjaw temporarily (in some cases, permanently) loses the ability to open and/or close the mouth. Some cases of lockjaw can cause extreme pain and discomfort. Knowledge of the normal range of mouth opening is essential in the diagnosis and treatment of lockjaw. It varies with people and is usually within a range of 40-60 mm. Two (~40 mm) to three fingers breadth (~54-57 mm) is the usual width of the opening. Lockjaw is often diagnosed when a mouth opening of less than 20 mm. Other classifications include:

  • The mouth opening of greater than 30 mm but lesser than 40 mm indicates light trismus.
  • The mouth opening of 15-30 mm indicated moderate trismus.
  • The mouth opening of lesser than 15 mm indicates severe trismus (less than 1 fingerbreadth).

Some common symptoms that arrive in tandem with lockjaw are:

  • Earaches or ear ringing
  • Headaches
  • Jaw popping or jaw clicking
  • Clenching the teeth
  • Weakness when chewing, speaking or yawning
  • The top and bottom teeth feel like they don’t fit together well
  • Facial pain


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What to do when I have an episode of lockjaw?

The following things can help relax the joint to get some relief:

  • Apply heat to loosen muscles. For mild to moderate cases of lockjaw, a warm compress can reduce stress and pain.
  • Take an anti-swelling and painkiller medication, such as Acetaminophen and Ibuprofen, to reduce the swelling.
  • Consider an appliance, such as a night guard, to limit the damage caused by grinding.
  • Lower stress levels to minimize clenching.

What are the treatment options for lockjaw?

The five treatment options of lockjaw may include:

  • Many times, people experiencing lockjaw or TMJ disorder can obtain relief by incorporating self-care strategies into their lives. Paying attention to oral hygiene to prevent gum infections and carries can help prevent inflammation of the jaws.
  • Many doctors may recommend medications to reduce pain, stress, and muscle tension. Surgery is sometimes employed in difficult cases. A combination of techniques is often the best treatment.
  • Vaccination against tetanus is an important step in preventing lockjaw.
  • Studies show success in treating lockjaw with low-level laser therapy, transcutaneous electrical nerve stimulation (TENS), ultrasounds, and trigger point injections.
  • Splints or night guards are commonly prescribed by dentists, and massage and physical therapy may be beneficial as well.

Lockjaw can dramatically affect the quality of life in a variety of ways. Communication is more difficult when one is suffering from lockjaw. It is difficult to speak with the mouth partly closed, thus impairing articulation. Also, lockjaw can decrease the size of the resonating oral cavity, diminishing vocal quality. Severe lockjaw makes it difficult or impossible to insert dentures. It may make physical re-examination difficult if a limited mouth opening precludes adequate visualization of the site. Oral hygiene is compromised, chewing and swallowing are more difficult, and there is an increased risk of aspiration.

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Medically Reviewed on 1/31/2022
Health Online Unit. Lockjaw. Ministry of Health Malaysia. http://www.myhealth.gov.my/en/lockjaw/