Often associated with the bacterial infection Tetanus, lock jaw is one of a number of disorders that can affect the jaw, causing a range of uncomfortable symptoms for sufferers. While most cases are temporary and able to be treated easily, lock jaw can sometimes be a sign of a more serious underlying illness, so it is important to seek prompt medical treatment.

In this guide to lock jaw, we discuss what lock jaw is, the main symptoms and lock jaw causes, and provide advice about how to unlock a locked jaw.

What is lock jaw? And what are the main lock jaw symptoms?

Lock jaw, or trismus as it is known medically, is a disorder that causes the jaw muscles to spasm, preventing the mouth from opening properly. Most cases of lock jaw are temporary, with symptoms typically peaking within a few hours, and lasting for less than two weeks.

The locking sensation that lock jaw causes typically affects the entire jaw and results in a range of painful symptoms that are felt on both sides of the face. The main symptoms of lock jaw include:

  • Jaw locking – the defining symptom of lock jaw is the jaw not opening fully, typically to less than 35mm. This jaw locking may also prevent sufferers from fully closing their mouths
  • Jaw pain and cramping, caused by spasming jaw muscles
  • Difficulty biting, chewing and swallowing due to limited jaw mobility
  • Difficulty talking, which may make it hard for other people to understand you
  • Headache, due to increased tension within the jaw
  • Earache

Because lock jaw prevents sufferers from opening their mouths, it can have a secondary effect of causing poor oral hygiene. Sufferers are often unable to swallow properly, and can’t practice their usual dental care routines, which may result in halitosis (bad breath), dry mouth and oral inflammation.

Main lock jaw causes

Lock jaw occurs as a result of spasms in the jaw muscles, so anything that causes intense jaw muscle spasms can cause lock jaw. Often, you’ll see the term ‘lockjaw’ used interchangeably with Tetanus. While lock jaw is one of the main symptoms of Tetanus, this bacterial infection is not the only cause of lockjaw.

The main lock jaw causes include:

Temporomandibular joint (TMJ) disorders

Temporomandibular joint (TMJ) disorders can cause inflammation of the soft tissues surrounding the jaw, sometimes resulting in jaw locking. The temporomandibular joint connects your jawbone to your skull. TMJ disorders refer to disorders that cause this joint to malfunction, and typically result in pain in the jaw joint and muscles that control the jaw, as well as headaches and jaw clicking or popping when moving your jaw. In particularly severe cases, lock jaw may occur as one of the symptoms. Risk factors for developing TMJ disorders include chronic teeth grinding and clenching, injury to the jaw, rheumatoid arthritis and osteoarthritis, and certain connective tissue disorders.


Medical conditions that cause oral inflammation, or inflammation in the jawbone may cause jaw locking. Examples include pericoronitis, which is inflammation in the soft tissue around a tooth, arthritis, scleroderma—an autoimmune disease that affects connective tissue—and soft tissue fibrosis.


Tetanus is a serious disorder of the central nervous system caused by infection with the Clostridium tetani bacterium. It is often called ‘lockjaw’ as toxins released by the bacterium result in severe muscle contractions, particularly of the jaw and neck muscles, that cause jaw locking. Infection in Australia is relatively rare due to high vaccination rates, however it can still occur if spores from the bacterium make their way into someone’s body through broken skin (e.g. getting dirt in a wound, or stepping on a nail). There is no cure for tetanus, so treatment focuses on managing symptoms until the effects of the toxins resolve. If you suspect you may have, or be at risk of developing Tetanus you should seek prompt medical attention.

Trauma to the jaw

Trauma to the jaw that results in injury or damage can cause jaw locking. Common examples of trauma to the jaw that can cause lock jaw include fractured jawbones and tissue damage as a result of dental surgery.

Dental surgery

Dental surgery, such as a wisdom tooth extraction, can lead to jaw locking if it causes inflammation in the mouth, or results in hyperextension of the jaw. Hyperextension refers to the jaw being open beyond its typical range of motion.


Certain medications can cause lock jaw as a side-effect. This typically occurs as the medications alter nerve functioning. Examples of medications that may cause jaw locking include anti-nausea medications and some antipsychotic medications.

Cancer and cancer treatments

Cancer and cancer treatments (such as surgery and radiation) can cause jaw locking if they result in injury to certain parts of the jaw that control movement. Head or neck cancers are the most common cancer types associated with lock jaw.

Other infections

Tetanus is not the only infection that can cause lock jaw. Other infections such as mumps, tonsillitis and abscesses including peritonsillar abscesses can also cause jaw locking by resulting in inflammation.

Other causes

Other causes of lock jaw can include low calcium levels (hypocalcemia) and nerve or muscle diseases that result in muscle spasms.

Because there is such a wide range of lock jaw causes, it is important to consult your healthcare professional to determine what is causing your jaw locking.

How is lock jaw diagnosed?

If you suspect you might have lock jaw, it’s important to see a healthcare professional as they will be able to make a proper diagnosis. Not only will they be able to provide relief of the lock jaw symptoms, but also identify any underlying illnesses that may be causing the lock jaw.

Lock jaw is typically diagnosed by a healthcare professional based on a physical examination and an assessment of your medical history. During the physical examination, your doctor will likely consider the following:

  • How wide you can open your mouth. Most healthy people can usually open their mouths between 35 and 55mm (or 1.4 to 2.2 inches) wide. However, lock jaw sufferers can typically only open their mouths 35mm (1.4 inches) at the most.
  • How easily you can open and close your mouth. Patients suffering from lock jaw are often unable to fully close their mouths and have difficulty opening them.
  • Stiffness and tightness in the muscles in your jaw and neck.
  • Any problems you might have with your teeth, such as clenching.

When considering your medical history, your doctor will look for factors that point to an underlying illness. If necessary, they may request additional testing such as blood tests to rule out infections, or imaging studies to identify any injuries or tumours that may be affecting the jaw.

Because lock jaw can make it difficult to speak, it may be helpful to take someone with you to the appointment so they can explain your medical history on your behalf.

How to unlock a locked jaw?

Fortunately, most cases of lock jaw can be successfully treated through a combination of medication and physical therapy. However, it’s important to seek help as soon as possible, as the earlier a person begins treatment, the better the outcome.

In terms of how to unlock a locked jaw, treating lock jaw typically involves both alleviating the condition’s primary symptoms, and addressing the underlying cause of the lock jaw. In many cases, lock jaw treatment involves a combination of muscle relaxants and physical therapy.

Muscle relaxants are used to provide relief from the painful muscle spasms that commonly cause lock jaw. Depending on the nature of the lock jaw, oral muscle relaxants or injected muscle relaxants will be used. Common examples of medications used to treat lock jaw include Flexeril (Cyclobenzaprine) and Skelaxin (Metaxalone), while injected muscle relaxants may include Botox or anti-inflammatory steroids. Because injected muscle relaxants only target the specific site of spasm, they typically do not cause the drowsiness that may be associated with oral medications.

Physical therapy is also commonly used to help relax the jaw and return it to normal functioning. Physical therapy for lock jaw typically involves performing a series of specific mouth exercises. These are similar to other TMJ exercises that may be recommended to help alleviate the pain associated with TMJ disorders. In some cases, a doctor may also recommend the use of a jaw stretching device to encourage greater mobility and flexibility in the sufferer’s jaw joint and tissues.

Home remedies for lock jaw

The most appropriate treatment for each case of lock jaw depends on the underlying cause, so it is vital to see your healthcare professional to develop a treatment plan. However, there are a number of helpful remedies you can use at home to get some relief. These include:

  • Applying a warm compress to your jaw and/or neck. Doing this several times a day for around 20 minutes per session can help relieve muscle stiffness by encouraging more blood to flow to your jaw. You can use a heat pack, hot water bottle, or warm towel.
  • Applying a cold compress to your jaw and/or neck. If the pain is severe, using a cold compress may be a good option to numb the pain. Freezer bricks or ice wrapped in a tea towel work well if you don’t have a medical cold pack. Just make sure to never apply the ice directly to your skin.
  • Self-massage. Gently massaging your jaw muscles after you have used a warm compress can help to reduce tightness. Apply a small amount of massage oil to your fingertips and gently rub the muscles next to your ears in a circular motion.
  • Switching to a soft food diet. Hard, chewy or crunchy foods that place pressure on your jaw can aggravate your lock jaw symptoms. While experiencing and recovering from lock jaw, eating soft foods (such as soups, pureed vegetables and yoghurt etc.) can take some pressure off your jaw. You also won’t need to open your mouth as wide to eat these foods.
  • Staying hydrated. Keeping hydrated is vital for proper muscle function. If you are having trouble drinking due to lock jaw, try using a straw.
  • Ensure you are getting an adequate amount of calcium and magnesium in your diet. Calcium and magnesium are two minerals integral to proper muscle function, as they play an important role in helping your muscles to relax. The best way to achieve the recommended daily intake of calcium and magnesium is by eating a balanced diet, as numerous foods are rich in these minerals. However, if required, both calcium and magnesium are available as supplements.

How is lock jaw different from other TMJ disorders?

Lock jaw is one of a number of disorders that can affect the jaw. One of the most common of these is called a TMJ disorder. TMJ disorders cause pain and discomfort in the temporomandibular joint, which connects the jawbone to the skull. While a locked jaw can be one symptom of a TMJ disorder, they typically have other milder symptoms.

Some key differences between lock jaw and TMJ disorders are:

  • The pain associated with a TMJ disorder is typically one sided, whereas lock jaw usually affects both sides of the jaw. In some instances, TMJ disorders may affect both sides of the jaw.
  • TMJ disorders may cause jaw stiffness and reduce the range of motion sufferers have in their jaw, particularly when yawning or laughing. They may also cause clicking of the jaw. However, this is typically milder than the freezing of the joint experienced with jaw lock which usually prevents the jaw from being opened more than 35mm.

Like lock jaw, the causes of TMJ disorders are varied, and include:

  • Bruxism, which is where people clench, grind or gnash their teeth. Over time this can place stress on the jaw, leading to TMJ disorders.
  • Damage or displacement of the cartilage disc that covers the TMJ’s surface. This can result in TMJ movement being disrupted. The cartilage disc may move out of place, or be damaged over time by arthritis.
  • Injury which damages the joint.

Because of the similarities between lock jaw and generalised TMJ pain, it’s best to see a doctor for a proper diagnosis.