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Updated on January 16, 2023
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Lockjaw: Causes, Symptoms & Treatment

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What is Lockjaw?

Lockjaw, also known as trismus, is a restricted ability to open the mouth. It typically involves painful spasms in the jaw muscles that control chewing. However, lockjaw can describe any limitation of normal mouth-opening movements, regardless of the cause.

The term “lockjaw” is commonly used as another name for tetanus, but this serious bacterial infection isn’t the only cause. Lockjaw has multiple causes and can be a joint or muscle problem. It’s usually temporary but can become permanent if not treated promptly. 

8 Potential Causes of Lockjaw

Here are some of the most common causes of lockjaw: 

1. Tetanus

A tetanus infection causes severe muscle spasms. Lockjaw is one of the first symptoms of tetanus. Other tetanus symptoms include trouble swallowing and painful neck and abdominal stiffness. 

Tetanus is a bacterial infection caused by clostridium tetani. These bacteria are commonly found in dirt, dust, saliva, or manure. When these substances contact an open wound, tetanus infection can develop. 

Tetanus can be lethal, with a 10 to 20% fatality rate, and there is no cure.1 Fortunately, the tetanus vaccine has made this serious bacterial disease rare in the U.S.

Treatment

Treatment for tetanus includes antibiotics and tetanus immune antiglobulin (TIg) to counter the toxin.

2. Temporomandibular Joint Disorders (TMD)

The temporomandibular joint (TMJ) connects the jaw (mandible bone) to the skull (temporal bone). You have a TMJ joint on each side of your jaw. It permits the lower jaw to move up and down, sideways, and front-to-back.

A TMJ disorder (TMD) is when the TMJ stops functioning properly. When a person with TMD tries to open their mouth, their jaw veers to the side. 

Other symptoms of TMD include:

  • Lockjaw
  • Jaw pain
  • Trouble chewing
  • Jaw popping or clicking

TMD affects anywhere from 5 to 12% of the population.9 Symptoms usually pass on their own, but various treatments are available. Talk to your doctor if you think you have TMD.

Treatment

Treatment options for TMD include:

  • Oral appliances
  • Behavioral therapy
  • Relaxation techniques
  • Antiinflammatory medications
  • Physical therapy
  • Surgery (in rare cases)
  • Botulinum toxin (Botox®) injections

3. Infections

Lockjaw can be caused by dental infections and non-oral infections, including:4, 12

  • Tonsilitis
  • Dental abscess
  • Brain abscess
  • Meningitis
  • Osteomyelitis of the mandible
  • Gonorrhea
  • Mumps

Symptoms and treatment vary based on the type of infection.

4. Congenital Conditions

Some people are born with conditions that make them more prone to lockjaw. Examples include:

  • Pierre-Robin sequence
  • Trismus-pseudocamptodactyly syndrome

5. Cancer

Trismus is a common complication of cancer, especially cancers of the head and neck. Tumors that originate in or metastasize to the mandible—and the muscles involved in chewing—can cause lockjaw.

6. Inflammation

Inflammation can cause restricted movement in many joints, including the TMJ. Inflammatory conditions that may lead to lockjaw include:

  • Osteoarthritis
  • Rheumatoid arthritis
  • Soft tissue fibrosis
  • TMJ ankylosis
  • Scleroderma
  • Temporal arteritis
  • Infections such as a peritonsillar absecess 

7. Certain Drugs and Medical Treatments

Drugs and medical treatments that have been shown to cause trismus include:11

  • Radiotherapy for head and neck cancer
  • Tricyclic antidepressants
  • Metoclopramide (used to treat tardive dyskinesia)
  • Phenothiazines (anti-psychotic)
  • Local anesthesia

8. Trauma

Injuries to the mandible and chewing muscles can lead to lockjaw. These include:

  • Jaw fractures and dislocations
  • TMJ injury
  • Complications of jaw surgery and other dental work

Signs and Symptoms of Lockjaw

The primary sign of lockjaw is the inability to open or close the mouth fully. This reduced range of motion typically affects the jaw joint on both sides of the face. It can happen suddenly and usually peaks within a few hours.

Other signs and symptoms of lockjaw may include:

  • Jaw pain or tenderness 
  • Neck or jaw muscle stiffness
  • Headache
  • Earaches
  • Difficulty or pain while chewing
  • Trouble swallowing
  • Difficulty speaking
  • Jaw clicking or popping 
  • Facial swelling

How to Tell if You Have Lockjaw

Trismus is diagnosed if a person can’t open their mouth 35 or more millimeters.11 

One simple test you can do at home is to insert three fingers vertically between your upper and lower front teeth. This is roughly 35 millimeters in width. 

If you cannot fit all three fingers, that may indicate lockjaw.12

How Serious is Lockjaw? Is it Painful? 

Lockjaw can be a serious condition, depending on the cause. It can cause severe pain and trouble eating. If tetanus is to blame, lockjaw is a sign of a life-threatening disease. 

Other causes of lockjaw may not be life-threatening but can still cause problems. 

Potential Complications of Lockjaw

Lockjaw often causes the mouth to stay stuck in a slightly open position. After about a day, this can affect your oral health because you won’t be able to swallow or properly clean your teeth. This can lead to dry mouth (xerostomia).

You may also have problems communicating because people won’t be able to understand your speech.

If lockjaw persists for more than a few days, it can lead to complications that affect your overall health, such as:

  • Tooth decay and mouth ulcers
  • Teeth grinding (bruxism)
  • Malnutrition from the inability to chew or swallow

Without treatment, the jaw muscles can deteriorate. If this happens, lockjaw can become permanent.13

When to See a Doctor for Lockjaw

Seek immediate medical care if you experience difficulty opening your mouth or persistent painful muscle contractions in your jaw.  

Wash wounds contaminated with dirt or any other substance. Your doctor may also want you to get a tetanus booster shot.

Can Lockjaw Go Away on Its Own?

With proper managmenet, Lockjaw usually goes away within two weeks.11

However, lockjaw can sometimes be permanent. This can happen when a patient fails to do proper stretching exercises after radiation therapy or oral surgery.13

How is Lockjaw Diagnosed?

Diagnosis of lockjaw is based on a physical exam and a review of medical history (including vaccinations). Your doctor may check for TMD by placing their finger in your ear while you move your jaw.

Depending on the specific cause, you may then need to see a dentist or a TMJ specialist for treatment. 

How to Treat Lockjaw at Home

If you are dealing with a locked jaw and need immediate relief, here are some natural treatments and home remedies:

  • Heat and cold therapy — Alternate hot and cold compresses on the joint to reduce pain.
  • Over-the-counter medication — NSAIDs like aspirin or ibuprofen can reduce jaw muscle inflammation and provide pain relief.
  • Self-massage — Gently rub the muscles next to your ear to increase blood circulation and reduce muscle tension.
  • Gentle stretching — Try opening your jaw slightly and moving your mouth from side to side to unlock the jaw.
  • Correct your posture — Sit upright with a straight back and avoid sleeping on your side while your jaw is locked. You may want to try using a neck pillow at night.
  • Stay hydrated — This is important for overall health, not just lockjaw. Drinking enough water every day will help your jaw muscles stay healthy.
  • Eat healthy foods — Calcium and magnesium support a healthy nervous system and help the jaw muscles relax. These nutrients are found in nuts, seeds, and dark leafy greens.

Tips for Preventing Lockjaw 

Here are some tips for preventing lockjaw:

Get a Tetanus Vaccine

An easy way to prevent lockjaw from tetanus is to get vaccinated. Most people are vaccinated for tetanus during childhood. Medical experts agree adults should get booster shots every 10 years.8

Lower Your Risk for TMD

Some factors of lockjaw from TMD are genetic and outside a person’s control.14 However, there are certain things that you can do to make it less likely to develop.

Here are some tips to lower your risk for TMD:

  • Practice good posture
  • Wear a nightguard to prevent teeth from grinding
  • Refrain from chewing on objects (such as pens) or gum
  • Do gentle stretches to increase jaw mobility
  • When your face is at rest, keep your tongue at the top of your mouth and let your lower jaw hang loose
  • Speak with your dentist or physician about physical therapy options 
  • Learn facial muscle exercises

Do Prescribed Exercises

After oral surgery or radiation treatment on the jaw, follow your doctor’s medical advice regarding stretches and exercises.

Summary

Lockjaw is restricted mobility of the muscles and joints that open and close the mouth. The medical term for lockjaw is trismus. 

Because trismus is an early sign of tetanus infection, “lockjaw” is commonly used in reference to tetanus. However, many things can cause lockjaw, including temporomandibular joint (TMJ) disorders, infections, and radiotherapy to the head and neck area.

Tetanus can be fatal if left untreated, so it’s important to seek medical attention for painful jaw muscle spasms. Lockjaw is usually temporary and resolves within two weeks.

Last updated on January 16, 2023
15 Sources Cited
Last updated on January 16, 2023
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
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  14. Smith, SB., et al. “Potential Genetic Risk Factors for Chronic TMD: Genetic Associations from the OPPERA Case Control Study.” The Journal of Pain, 2012.
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  16. Scully, C. “Trismus.” Oral and Maxillofacial Medicine: The Basis of Diagnosis and Treatment, Elsevier, 2012.
  17. Wu, VWC and Lam, Y. “Radiation-induced temporomandibular joint disorder in post-radiotherapy nasopharyngeal carcinoma patients: assessment and treatment.” Journal of Medical Radiation Sciences, 2016.
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