An Overview of Lockjaw

Tetanus Is One of the Causes of Lockjaw

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Lockjaw, which is also sometimes called trismus, is a condition in which a person's jaw muscles spasm. If you develop lockjaw, your jaw may be "frozen" in a certain position, and you might not be able to open your mouth wide. Lockjaw can occur in association with a variety of health conditions, including cancer treatment, tetanus, and as a medication side effect.

Lockjaw can be painful, and it can cause complications, such as choking. Treatment includes oral (by mouth) or injected muscle relaxants. Sometimes, physical therapy is needed to help regain muscle control.


Lockjaw affects the whole jaw and is usually equal on both sides. It can occur suddenly, reaching its peak effect over the course of a few hours. While an inability to open your mouth fully is the most common symptom of lockjaw, several other effects can occur as well.

When you can't control your mouth, your speech may be difficult for others to understand and you can have trouble swallowing,

Within just a few hours, lockjaw is associated with:

After about a day, lockjaw can affect your oral health because you can't swallow saliva. Effects of lockjaw include

If you experience lockjaw for a longer than a few days, it can affect your overall health. Complications of persistent lockjaw include:

  • Tooth decay and ulcers in your mouth can develop when you can't effectively brush your teeth and floss.
  • Bruxism (teeth grinding) can cause your tooth enamel to wear away, and may even cause your teeth to crack.
  • You can become malnourished due to difficulty eating.
  • A muscle contracture is stiffening of the muscle and is characterized by a change in the muscle structure, which does not respond to treatment as easily as a muscle spasm.


Lockjaw occurs when muscle spasms inhibit control of your jaw movements. A muscle spasm is a condition in which a muscle remains in its active position and cannot relax. This can occur due to an injury to the muscle, nerve, bone, tendon, or ligament.

There are several risk factors that predispose to lockjaw, including:


Cancer and some cancer treatments (surgery or radiation) can cause injuries to the structures that control your jaw movement. If you have had head or neck cancer, or have had surgery or radiation treatment for head or neck cancer, you have about a 30 percent chance of developing lockjaw.

Temporomandibular Joint Disorders

Your temporomandibular joint is located at the sides of your face, below your eyes and towards your ears. This joint is where the muscles, bones, tendons, and ligaments that control your jaw meet.

Temporomandibular joint disorders, often called TMJ, can develop due to arthritis, inflammatory disease, or facial trauma. TMJ commonly results in lockjaw. Because TMJ is often a chronic condition, lockjaw can recur even after it resolves.


Infections in and around your mouth or jaw muscles, such as a peritonsillar abscess, can affect the movement of the jaw, resulting in lockjaw. In rare instances, your nerve or muscle can become permanently damaged due to an infection, potentially predisposing to recurrent episodes of lockjaw.


Some medications can affect nerve function and may predispose or cause lockjaw. Reglan (metoclopramide) and some antipsychotic medications are the most common culprits. Rarely, anesthetics can cause a rare complication called malignant hyperthermia, which can cause muscle spasms, including lockjaw.

Medical Conditions

Sometimes, nerve or muscle disease can cause muscle spasms. For example, stiff person syndrome, a rare autoimmune disorder, can cause spasms in any voluntary muscle, including the jaw muscles.


Tetanus occurs due to a life-threatening neurotoxin that is released by Clostridium tetani, a bacterium commonly present in the environment. Tetanus toxin can cause muscle spasms, which may affect the heart muscles, chest muscles (impairing breathing), or any voluntary muscles in the body, including the jaw muscles.

Tetanus is a huge risk factor for lockjaw. In fact, lockjaw used to be called tetanus. However, in most parts of the world, tetanus is extremely rare because immunizations and booster shots that protect against the infection are routine. While it almost always causes lockjaw, immunizations have made tetanus among the least common causes of the condition.

There are a number of nerves and muscles that control jaw movement, and due to their anatomical arrangement, lockjaw is typically characterized by a jaw position that is partially open.


Lockjaw is diagnosed based on your medical history and your physical examination. The effects can make it difficult for you to verbally explain your symptoms to your medical team, so most people have to describe their medical history by writing it down.

Physical Examination

Normally, most people can open their mouth between 35-55 mm or 1.4 to 2.2 inches wide. If you have lockjaw, you may only be able to open your mouth less than 35 mm (1.4 inches). This distance is less than 3 fingers in width.

If you have lockjaw, you might not be able to close your mouth all the way, and you are likely to have trouble moving your jaw. Your doctor may also detect stiffness and tightness of your jaw muscles, and your teeth may be clenched.

Diagnostic Tests

If there is a concern that you could have an injury, infection, or tumor affecting your mouth, face, or jaw, you may need to have diagnostic testing. Imaging studies, such as x-rays, computerized tomography, (CT), ultrasound or magnetic resonance imaging (MRI) can often identify lesions in and around the jaw.

In some instances, a biopsy is needed so that your medical team can more closely examine a tumor.


Lockjaw can be treated with medication and/or physical therapy. Types of practitioners that treat this condition include otolaryngologists, dentists and oral surgeons. Oral muscle relaxants and injected muscle relaxants are typically helpful. If your muscle spasm was caused by medication, then discontinuing it is recommended as well. And treatment of the underlying problem (such as an infection) is typically necessary.


Muscle relaxants such as Flexeril (cyclobenzaprine) or Skelaxin (metaxalone), which are taken orally, can help alleviate the muscle spasms of lockjaw. They may, however, cause side effects, such as drowsiness.

Targeted injections, including botulinum toxin or anti-inflammatory steroids, can relax the muscle, relieving the spasm. Injections require scheduling an interventional procedure, and they do not cause systemic side effects of oral medications.

Treating the Underlying Problem

If your lockjaw is caused by a medical problem, you will need treatment for the cause of your lockjaw. For example, infections may necessitate oral or intravenous (IV) antibiotics. TMJ may require anti-inflammatory treatment. And tumors may require radiation or surgery.

If radiation therapy or surgery is the cause of your lockjaw, then physical therapy may be the most effective treatment approach.


In addition to medical management, you may need physical therapy and/or speech therapy. Your therapist may also suggest at-home exercises so you can improve control of your jaw muscles. When you take part in at-home therapy, is important to avoid pushing your exercises to a painful level.

A Word From Verywell

If you have experienced lockjaw, you may be at risk for developing it again, so it is important to discuss prevention with your doctor. Preventative strategies may include avoiding medications that trigger it, getting treatment for your TMJ, and maintaining regular exercise of your jaw muscles. Most importantly, if you notice the symptoms acting up, you should seek medical attention promptly to avoid contractures or other complications.

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