Causes, What It Feels Like, and How to Stop It

How to stop lockjaw depends on its cause. Lockjaw, also known as trismus, is not always caused by tetanus. It can also result from trauma, temporomandibular joint (TMJ) disorders, oral infections, or even some medications. Treatment usually includes muscle relaxants to ease tension and specific exercises to help the jaw move more easily.

Physical therapy is crucial in treating lockjaw, as it helps improve jaw flexibility and reduce stiffness. Doing exercises at home several times a day can gradually enhance jaw movement. However, if you experience severe pain or if the lockjaw prevents you from opening your mouth, it’s important to seek immediate medical attention for an accurate diagnosis and proper treatment.

Symptoms

The defining symptom of lockjaw is only being able to open your mouth about 35 mm (1.4 inches)—that’s less than three fingers in width.

Lockjaw affects the whole jaw. The “locking” of the jaw is usually felt equally on both sides of the face. Lockjaw can come on suddenly, and the symptoms peak within a few hours.

Many nerves and muscles control the movement of your jaw. Lockjaw typically causes your jaw to be partially open because of where these nerves and muscles are located.

While not being able to open your mouth fully is the most common symptom of lockjaw, it’s not the only symptom. Lockjaw can last from several hours to a few days. Within just a few hours, lockjaw can also cause:

• Headaches
• Jaw pain
• Pain in the neck area
• Swelling of the jaw
• Earaches
• Muscle spasms

Lockjaw can make your speech hard for others to understand. You may also have trouble swallowing because you cannot control your mouth’s movement.

After about a day, lockjaw will start to affect your oral health because you will not be able to swallow your saliva normally or take care of your teeth dry mouth (xerostomia), and a sore, inflamed mouth (mucositis).

Lockjaw that lasts for longer than a few days can affect your overall health. Complications of persistent lockjaw include:

Causes

Lockjaw occurs because a muscle remains in its active position and cannot relax (spasm). The muscle spasm that occurs with lockjaw can be caused by many things.

For example, a spasm can happen when there is an injury to the muscle, nerve, bone, tendon, or ligament. It can also be related to health conditions, infections, and medications.

Temporomandibular Joint (TMJ) Disorders

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

The TMJ allows you to chew food, speak, and yawn. TMJ disorders are chronic conditions that can lead to lockjaw.

TMJ can develop for multiple reasons, including:

If you experience lockjaw because you have TMJ, being dehydrated can trigger a flare or make your symptoms worse. Lockjaw from TMJ can come back even after the initial discomfort of the chronic condition goes away.

Oral Infections

Infections around your mouth or jaw muscles, such as a peritonsillar abscess, can affect the jaw’s movement. When this happens, lockjaw can occur.

In rare instances, your nerve or muscle can become permanently damaged from an infection. If it does, you might be more likely to experience recurrent episodes of lockjaw.

Medication

Some medications can affect nerve function and lead to lockjaw. The most common culprits are anti-nausea medications, such as Reglan (metoclopramide), and some antipsychotic medications.

Rarely, anesthetics can cause a rare condition called malignant hyperthermia. This complication is a severe reaction where a person gets a high body temperature and rapid heart rate. In addition, it can involve muscle spasms, including lockjaw.

Cancer

Cancer and some cancer treatments (e.g., surgery, radiation) can cause injuries to parts of the jaw that control movement.

There are a few risk factors for developing lockjaw during cancer treatment:

• Head or neck cancer
• Surgery for head or neck cancer
• Radiation treatment for head or neck cancers

If you have head or neck cancer or have had treatment for these types of cancers, you have about a 30% chance of developing lockjaw.

Tetanus

In the past, the term “lockjaw” was used as another name for tetanus, a serious bacterial infection. Lockjaw is now defined as the sustained locking of the jaw by any cause. This could include trauma, surgery, medication side effects, mouth infections, dental problems, and cancer or cancer treatment.

Lockjaw can be extremely painful and, in some cases, life-threatening. When tetanus is involved, lockjaw can lead to complications such as choking, the inability to breathe, and death.

Tetanus occurs when a person is exposed to a life-threatening neurotoxin that’s released by a bacterium. The bacterium, Clostridium tetani, is commonly found in the environment.

Tetanus toxin can cause muscle spasms in several muscle groups, including:

• Heart muscles
• Chest muscles (which impairs breathing)
• Facial muscles (including those of the jaw)
• Any voluntary muscles in the body

Tetanus is a significant risk factor for lockjaw. Most people with tetanus experience it.

However, tetanus is extremely rare in most parts of the world because tetanus shots are routine immunizations that protect against the infection.

Bruxism

Bruxism is a common movement disorder characterized by the repetitive clenching of the jaw and grinding of the teeth. Bruxism can occur when a person is awake or asleep.

People with sleep bruxism commonly awake with restricted jaw movement. Other common symptoms of bruxism include:

• Jaw pain and discomfort
• Jaw stiffness
• Jaw tension and muscle fatigue
• Headaches
• Facial pain
• Disrupted sleep
• Tooth wear
• Tooth fractures

The exact cause of bruxism is poorly understood. However, it is strongly linked to psychological stress and anxiety. People with aggressive, hurried, and competitive personality types appear more likely to experience bruxism. It has also been linked to the use of some antidepressant medications.

Other Medical Conditions

Low calcium levels (hypocalcemia) are another common cause of lockjaw. This complication can sometimes happen during thyroid surgery.

Nerve or muscle diseases can also cause muscle spasms. For example, a rare autoimmune disorder called stiff person syndrome can cause spasms in any voluntary muscle, including in the jaw.

When to See a Healthcare Provider

See a healthcare provider if you suddenly develop lockjaw which cannot be explained by a previous diagnosis. You should also see a provider right away if you have lockjaw and:

• Your jaw is locked in one position
• The jaw pain spreads to your face or neck
• You have difficulty eating, drinking, or swallowing
• The lockjaw developed after an accident, injury, or recent dental work
• Your jaw or face is swollen
• Home remedies or over-the-counter pain medications do not ease the pain
• You experience muscle spasms elsewhere in your body
• You recently started a new medication

Some lockjaw symptoms like neck pain may also indicate other serious conditions. For an accurate diagnosis, it’s always best to consult a healthcare provider.

Diagnosis

Providers can diagnose lockjaw based on your medical history and a physical examination.

However, lockjaw can make it hard for you to verbally explain your symptoms because you are not able to speak clearly. You may need to write down your symptoms or have someone else give your medical history to a provider.

Physical Examination

Most healthy people can open their mouths between 35 to 55 millimeters (mm) or 1.4 to 2.2 inches wide. If you’re experiencing lockjaw, you might only be able to open your mouth less than 35 mm (1.4 inches)—or less than three fingers in width. Your healthcare provider will measure how wide your mouth can open to see if you fall in or out of the typical range.

Your provider will also look for other signs of lockjaw, such as:

• Your ability (or inability) to close your mouth all the way
• Trouble moving your jaw
• Stiffness and tightness of your jaw muscles
• Clenched teeth

Tests

If there is a concern that you could have an injury, infection, or tumor affecting your mouth, face, or jaw, you may need more diagnostic testing.

Imaging studies can often identify lesions in and around the jaw. They might include:

Blood tests, including blood cell counts and electrolyte balances, may be important. You may need to have a piece of a tissue removed so that it can be looked at more closely with a microscope (biopsy).

Treatment

Lockjaw can often be treated with an oral or injected muscle relaxant. Physical therapy is also commonly part of a treatment plan for lockjaw.

If you have another condition that’s causing lockjaw, you’ll need treatment for that as well. For example, if you have an infection, you may need to take antibiotics.

You may need to work with different healthcare providers to treat lockjaw, including the following:

• Otolaryngologist (ENT)
• Dentist
• Oral surgeon

If a medication you’re taking caused your muscle spasm, your provider will likely recommend that you stop. However, never stop a medication without your provider’s OK.

Spasm Relief

Oral and injected muscle relaxants are typically helpful for lockjaw.

Common examples of oral medications that relax muscles include:

However, these medications may cause side effects such as drowsiness.

Targeted injections for lockjaw, including botulinum toxin (Botox) or anti-inflammatory steroids, can help relax the muscle and relieve the spasm. The injections do not cause the body-wide side effects that can happen with medications.

Physical Therapy

In addition to medical management, you may need to have physical therapy or speech therapy for lockjaw. Your therapist may also suggest at-home exercises to improve control of your jaw muscles.

Some exercises may involve a jaw-mobilizing device, which is often recommended for TMJ disorders. These devices help improve jaw movement by gently pressing on the jaw joints and muscles to reduce stiffness and pain.

If you’re doing at-home therapy for lockjaw, don’t push yourself so hard that the exercises are painful. Your therapist may recommend at-home exercises like these:

• Smile stretch: Try to smile as wide as possible without pain. While smiling, open your jaw about two inches. Do five to 10 repetitions, taking care to breathe between repetitions.
• Tongue pressure stretch: Place the tip of your tongue on the roof of your mouth and apply gentle pressure. Slowly open your mouth as wide as you can without pain then close it slowly. Perform each repetition for about 30 seconds each. Repeat two to three times.
• Side-to-side jaw movements: With your mouth slightly open, move your jaw from side to side in small, controlled motions. Do this for 30 seconds, two to three times.

It’s important to seek a healthcare provider’s evaluation before performing lockjaw exercises. They will help tailor your exercise regimen to fit your specific treatment needs.

Treating the Underlying Cause

Since there’s a wide range of conditions that can cause lockjaw, there’s also a range of treatments that might be required to address them. For example:

• Oral or intravenous (IV) antibiotics for infections
• Anti-inflammatory treatment for TMJ
• Radiation or surgery for tumors

If radiation therapy or surgery is the cause of your lockjaw, then physical therapy might be the most effective treatment approach. However, longstanding lockjaw after radiation therapy can be very hard to reverse.

Prevention

If you have experienced lockjaw, you are at risk for developing it again. It’s important to discuss prevention with your healthcare provider. Preventative strategies for lockjaw may include avoiding medications that trigger it, treating TMJ, or practicing jaw exercises.

• Tetanus boosters: Lockjaw from tetanus can be prevented with a tetanus shot. Tetanus immunizations are given in early childhood as part of the five-dose DTaP series given between 2 months and 6 years old. Children should receive the Tdap booster shot around age 11. Then, a tetanus booster is needed every 10 years. 
• Medications: Some medications are linked to lockjaw symptoms, including antipsychotic medications known as dopamine receptor 2 (D2) antagonists and the anti-nausea medication Reglan (metoclopramide). If you experience lockjaw as a medication side effect, talk to your healthcare provider about other options.
• Jaw exercises: Physical therapy exercises for TMJ can help to prevent a recurrence of lockjaw when caused by TMJ.
• Self-care techniques such as resting the jaw, avoiding difficult-to-chew foods, and applying a warm compress can also help with TMJ.

Summary

Lockjaw is a condition where the muscles in the jaw affect its movement. The mouth is not able to open as widely as usual, which can affect speech and swallowing. Temporomandibular joint disorders, oral infections, medications, cancer, bruxism, tetanus, and other medical conditions can cause lockjaw.

Treatment for lockjaw is aimed at relaxing the muscles and getting them moving normally again, as well as addressing the root cause. Physical therapy, at-home exercises, and medication are common components of a treatment plan for lockjaw.