Medically Reviewed By William C. Lloyd III, MD, FACS
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What is lockjaw?

Historically, the term lockjaw was used interchangeably with tetanus. One of the telltale signs of tetanus was a tightening or contraction of the jaw muscles. The medical term for this symptom is trismus. A bacterial infection with Clostridium tetani causes lockjaw from tetanus. It’s a very serious infection that kills about 20% of people who get it. Fortunately, vaccines have essentially stopped tetanus and the deaths it caused. Today, the United States sees about 30 cases of tetanus each year. These days, people can still experience trismus, but the common causes are different.

Trismus, or lockjaw, is the inability to open the mouth or jaw to a normal degree. There are varying definitions of what exactly a normal mouth opening should be. In general, most people can open their mouth wide enough to insert three stacked fingers into it. Anything less than this could be due to trismus.

The jaw consists of two bones—the maxilla, or upper jaw bone, and mandible, or lower jaw bone. They meet at the temporomandibular joint (TMJ). A strong muscle—the masseter—connects the lower jaw bone to the skull. Various muscles and nerves work together to open and close the jaw. The muscles that close the jaw are 10 times stronger than the muscles that open the jaw. When nerves activate the closing muscles, they simultaneously tell the opening muscles to relax and vice versa. Lockjaw can occur when something causes an imbalance with the muscles, or something goes wrong with the nerves or the joint itself.

Lockjaw causes fall into several categories including:

  • Congenital syndromes
  • Head and neck cancer and its treatment
  • Dental conditions
  • Infections
  • Inflammatory conditions and nerve disorders
  • Trauma and jaw surgery

Lockjaw can be painful and can also make it difficult to chew, talk, practice oral hygiene, and even breathe. Depending on the cause, these symptoms can develop suddenly or gradually. They can also be temporary or permanent.

Doctors can usually diagnose trismus with a physical exam. Early treatment is the best way to prevent it from becoming severe. Lockjaw treatments have two goals. The first is to correct the underlying cause, if possible. The other is to relieve symptoms using heat, pain relievers, and muscle relaxants among other strategies. Physical therapy may be necessary in some cases.

Seek prompt medical care if you develop jaw stiffness, jaw spasms, or problems chewing. The sooner you begin treatment, the more effective it is likely to be.

What other symptoms might occur with lockjaw?

For many people, lockjaw symptoms tend to develop and progress slowly. This can make it hard to tell there is a problem until you can only open your mouth about halfway. In some cases, the symptoms start rather suddenly. It depends on the underlying condition.

Jaw-related symptoms that may occur along with lockjaw

The main symptom of lockjaw is being unable to fully open your mouth. There are differing measures of what a normal mouth opening should be. Most are somewhere around 30 to 40 mm (millimeters). or about 1.2 to 2.0 inches. Other common lockjaw symptoms include:

  • Inability to brush and floss your teeth effectively
  • Jaw, facial, gum or tooth pain
  • Problems chewing, talking or breathing
  • Spasms or tightness when opening the mouth
  • Swelling

Other symptoms that may occur along with lockjaw

Depending on the cause, other symptoms may include:

  • Choking
  • Hearing problems or hearing loss
  • Voice changes

It’s important to seek medical care early when symptoms are ongoing and not getting better. Prompt treatment can help avoid serious and constant problems with lockjaw. It can be hard to treat once it becomes persistent.

What causes lockjaw?

Lockjaw, or trismus, happens when there is a problem with the muscles that move the jaw, the nerves that control the jaw muscles, or the jaw joint itself. There are several different categories of underlying causes of these problems.

Infectious causes of lockjaw

Infections may lead to trismus including:

  • Abscess in the mouth or neck area, including the salivary glands, throat, tonsils, and teeth and their supporting structures
  • Tetanus, which is rare today because of a vaccine to prevent it

Inflammatory causes of lockjaw

Trismus can originate from problems involving inflammation including:

  • Myositis, which is muscle inflammation

Neurologic causes of lockjaw

Problems with the nerves or nervous system can cause trismus including:

  • Brain stem disorders, including brain stem stroke
  • Drug toxicities and poisonings, such as phenothiazines, tricyclic antidepressants, metoclopramide and strychnine
  • Epileptic seizures, particularly status epilepticus
  • Parkinson’s disease
  • Trigeminal nerve damage

Traumatic causes of lockjaw

Trismus can arise from trauma including:

  • Burn injuries
  • Direct injury to the jaw muscles
  • Severe bruxism, which is teeth grinding and jaw clenching that can cause traumatic changes

Other causes of lockjaw

Other possible causes include:

  • Congenital disorders, including trismus-pseudocamptodactyly syndrome and Pierre-Robin sequence
  • Head and neck cancers
  • Impacted molars, including wisdom teeth
  • Muscle wasting around the jaw
  • Psychiatric problems, such as conversion disorder
  • Scarring or adhesions near the jaw or tongue
  • TMJ disorder

When should you see a doctor for lockjaw?

It’s important to see a doctor promptly if you notice problems opening your mouth or you experience jaw spasms, jaw stiffness, or other symptoms of trismus. Treatment is more likely to be effective when you start it early. Treatment will also be more comfortable if you address trismus before it progresses.

If you’ve had recent oral, head or neck surgery or treatment, contact the surgeon or provider’s office. Otherwise, see a primary care provider for an initial evaluation and referral if necessary. Seek prompt medical care (the same day) if you develop jaw stiffness, jaw spasms, or problems chewing.

How is the cause of lockjaw diagnosed?

Lockjaw is a clinical diagnosis, meaning doctors diagnose it by examining you and reviewing your medical history. There are no specific tests for it. However, doctors may use various tests to uncover the base cause of it. This may include imaging exams, such as X-rays, CT (computed tomography), and MRI (magnetic resonance imaging). These tests can reveal TMJ problems, fractures, tumors, and other physical abnormalities.

What are the treatments for lockjaw?

Lockjaw treatment has two goals. If possible, doctors treat the underlying condition that is contributing to lockjaw. Lockjaw due to tetanus will be treated with antibiotics. Doctors also use treatments to relieve pain and improve jaw movement.

When doctors expect trismus to be temporary, treatments may include heat therapy, NSAIDs (nonsteroidal anti-inflammatory drugs), and muscle relaxants. When trismus persists for more than a week, mouth stretching exercises may be necessary. These strategies are usually effective for trismus after surgery and other causes of acute lockjaw.

Some lockjaw causes are more chronic in nature and are likely to result in long-lasting problems with trismus. This kind of trismus is more resistant to conservative therapy. Examples include radiation therapy and scarring. In cases like these, doctors often recommend physical therapy.

A physical therapist may use electrical stimulation, deep heating, massage, and passive stretching exercises. Passive stretching does not involve using your jaw muscles. Instead, the therapist moves your jaw or you use a device that does the movement for you. Your therapist may also teach you how to stretch your jaw using your thumb and index finger.

Some people also need to see a speech therapist or a swallowing specialist to manage lockjaw.

Home remedies to prevent lockjaw

If you are at risk of developing lockjaw due to surgery or another condition, there are steps you can take to prevent trismus including:

  • Maintaining good posture and stretching your neck and shoulders.
  • Massaging your masseter muscles, which are the muscles under your cheekbone at the hinge of your jaw. Rub them with your first two fingers for 30 seconds at a time. Repeat 2 to 3 times a day.
  • Practicing good oral hygiene.
  • Relaxing your masseter muscles by trying not to clench them throughout the day.
  • Stretching your jaw muscles three times a day. Open your mouth as wide as you can and hold the stretch for 10 seconds. Then, move your jaw to one side and hold for three seconds before moving it to the other side and holding for three seconds. Next, move your jaw in a circle one direction and then the other. Repeat the exercises five times.

What are the potential complications of lockjaw?

In most cases, trismus is temporary and resolves with conservative treatment within two weeks. Chronic trismus, such as lockjaw from radiation therapy, can cause complications without adequate treatment. Being unable to open your mouth can lead to malnutrition and dehydration. It can also lead to dental problems, such as cavities and gum disease, when oral hygiene suffers. In severe cases, choking and aspiration pneumonia can occur.

The best way to prevent complications is to seek care early and follow your treatment plan. If you are at high risk for trismus due to head and neck cancer or its treatment, your doctor may recommend a mouth splint or other treatment to prevent trismus and its complications.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Mar 11
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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