Lockjaw is the inability to open the mouth to a normal extent.
Lockjaw has multiple causes and can be either a joint or muscle problem. It’s usually temporary but can become permanent if not treated promptly.
The medical term for a locked jaw is trismus. There are multiple causes behind trismus. Many of these are related to the temporomandibular joint (TMJ).
The TMJ connects the jaw to the skull. You have this on each side of your jaw. It permits the lower jaw to move up-and-down, sideways, and front-to-back.
When the TMJ stops functioning properly, this is known as a TMJ disorder (TMD).
A person with TMD who tries to open their mouth will find their jaw veers off to the side with the TMJ disorder. Other signs of a locked jaw due to TMD are jaw pain, trouble chewing, and clicking or popping noises.
According to health experts, TMD affects anywhere from 5 to 12% of the population.9
TMD may occur for multiple reasons. It may be caused by an injury or arthritis in the TMJ. The disk in the TMJ can sometimes slip out of alignment.
TMD can also be caused by inflammation of the soft tissue.3 Procedures such as radiotherapy and oral surgery can also cause TMD.17
Some other potential causes of trismus include:
Someone of any age can develop TMD, but those between the ages of 20 and 40 are particularly at risk.2 Other risk factors for TMD may include stress, arthritis, family history, and traumatic injuries such as jaw dislocation.
Symptoms of TMD usually pass on their own, but there are a variety of treatments available. Those who believe they are suffering from TMD should seek medical advice from their doctor.
Tetanus is a disease that causes severe muscle spasms. One of its earliest symptoms is a condition called trismus, which is the scientific term for lockjaw. For this reason, “lockjaw” is still commonly used as a synonym for tetanus.8
Cases of tetanus in the United States today are rare, as most people are vaccinated against the disease.
Contrary to popular belief, tetanus is not caused by exposure to rust.7 Tetanus is a bacterial infection caused by clostridium tetani. These bacteria are common in the environment, often found in dirt, dust, saliva, or manure. When an open wound is exposed to these substances, an infection can result.
Once tetanus is contracted, tetani bacteria attack the nervous system with a toxin. This toxin, known as tetanospasmin, prevents the spinal cord from transmitting signals to the muscles. This results in muscle spasms so intense they can fracture bones and cause damage to the muscles and spine.
The onset of symptoms for tetanus is between three and 21 days.
Besides trismus, these include trouble swallowing and painful stiffness in the neck and abdominal muscles. As the infection worsens, symptoms progress to fever, abnormal blood pressure, increased heart rate, and excessive sweating.
Difficulty breathing can also occur, with many patients requiring assistance from ventilators.
Tetanus can be a lethal disease, with a 10 to 20% fatality rate, with infants and the elderly particularly vulnerable.1 Complications include pneumonia, respiratory or cardiac arrest, and brain damage.1
There is no cure for tetanus. Once contracted, the only course is treatment of symptoms until tetanospasmin passes from the body.
Trismus is diagnosed if a person cannot open his mouth 35 or more millimeters.11 There should be anywhere from 35 to 55 millimeters (1.5 to 2.16 inches) between the tips of the upper and lower teeth.12, 13
For a person infected with tetanus, the distance between his upper and lower teeth may be reduced to between 10 to 20 millimeters.13
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 be an indication of lockjaw.12
Other signs and symptoms of lockjaw may include:
Lockjaw can be a serious condition, depending on the cause. It can cause severe pain and trouble eating. If it is due to tetanus, lockjaw is a sign of a life-threatening disease.
Lockjaw due to other causes may not be life-threatening but can still cause problems. It negatively affects personal appearance, oral health, speech, and proper nutrition.
Without proper treatment, deterioration of the jaw muscles can occur over time. If this happens, lockjaw can become permanent.13
If you experience difficulty opening your mouth or persistent pain or stiffness in your jaw muscles, seek medical attention immediately.
Wash wounds contaminated with dirt or any other substance. Your doctor may also want you to get a tetanus booster shot.
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.
Proper medical treatment for lockjaw depends on the cause. Some causes include:
First, the wound at the heart of the infection should be cleaned thoroughly. Antibiotics may be used to kill the bacteria. Tetanus immune antiglobulin (TIg) can be used to counter the toxin within the body.
While waiting for the toxin to be eliminated, muscle relaxants can be employed to control spasms. For other tetanus symptoms such as breathing trouble or heart issues, morphine may be administered.
If breathing becomes difficult, the patient may have to be placed on a ventilator. All this may take several weeks.
Doctors may prescribe muscle relaxants or even some antidepressants to help prevent bruxism. A mouthguard may also be used for this purpose.
Aside from medication, behavioral therapy can be done to address stress triggers. There are also stretching exercises for the jaw that can relieve tension and increase mobility.
Because symptoms of TMD usually resolve on their own, doctors generally don’t recommend surgery. However, in extreme cases, it is an option.
Surgeries used to address TMD include:
Botox is great for cosmetic treatments. But it is also effective at relaxing muscles and relieving tension and pain.
For example, botox is often used as a treatment to relieve TMD symptoms. It helps eliminate headaches and stress caused by lockjaw.
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
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 a booster shot every ten years to renew their tetanus immunity.8
After oral surgery or radiation treatment on the jaw, follow your doctor’s medical advice regarding jaw exercises.
Some of the factors for lockjaw from TMD are genetic and thus 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:
If you are dealing with a locked jaw and need immediate relief, here are some things you can do by yourself:
Centers for Disease Control and Prevention. “About Tetanus.” www.cdc.gov, 2019.
Gauer, Robert L, and Michael J Semidey. “Diagnosis and treatment of temporomandibular disorders.” American family physician vol. 91,no. 6 2015, pp. 378-86, www.aafp.org.
Ibi, Miho. “Inflammation and Temporomandibular Joint Derangement.” Biological & pharmaceutical bulletin, vol. 42, no. 4, 2019, pp. 538-542. Pubmed.ncbi.nlm.nih.gov.
Kim, Hyung-Mo, et al. “Infection of the temporomandibular joint: a report of three cases.” Journal of the Korean Association of Oral and Maxillofacial, vol. 37, no. 6, 2011. Synapse.koreamed.org.
Mayo Clinic. “Arthroscopy.” www.mayoclinic.org, 2020.
National Institute of Dental and Craniofacial Research. “Prevalence of TMJD and its Signs and Symptoms.” www.nidcr.nih.gov, 2018.
Smith, Shad B., et al. “Potential Genetic Risk Factors for Chronic TMD: Genetic Associations from the OPPERA Case Control Study.” The journal of pain, vol. 12, no. 11, 2011, pp. T92-101. www.ncbi.nlm.nih.gov.
Wu, Vincent W.C and Ying-na Lam. “Radiation‐induced temporo‐mandibular joint disorder in post‐radiotherapy nasopharyngeal carcinoma patients: assessment and treatment.” Journal of medical radiation sciences, vol. 63, no. 2, 2016, pp. 124-32. www.ncbi.nlm.nih.gov.