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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.
Here are some of the most common causes of lockjaw:
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 for tetanus includes antibiotics and tetanus immune antiglobulin (TIg) to counter the toxin.
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:
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 options for TMD include:
Lockjaw can be caused by dental infections and non-oral infections, including:4, 12
Symptoms and treatment vary based on the type of infection.
Some people are born with conditions that make them more prone to lockjaw. Examples include:
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.
Inflammation can cause restricted movement in many joints, including the TMJ. Inflammatory conditions that may lead to lockjaw include:
Drugs and medical treatments that have been shown to cause trismus include:11
Injuries to the mandible and chewing muscles can lead to lockjaw. These include:
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:
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
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.
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:
Without treatment, the jaw muscles can deteriorate. If this happens, lockjaw can become permanent.13
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.
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
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.
If you are dealing with a locked jaw and need immediate relief, here are some natural treatments and home remedies:
Here are some tips for preventing lockjaw:
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
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:
After oral surgery or radiation treatment on the jaw, follow your doctor’s medical advice regarding stretches and exercises.
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.
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