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What Causes Lockjaw?

Tricia Christensen
Updated Mar 03, 2024
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There are two medical conditions that are commonly referred to as lockjaw, and they have different causes. Trismus prevents the sufferer from opening his or her mouth normally, and its most common causes include inflammation of the muscles or tissues in the jaw area, a temporomandibular joint (TMJ) disorder or a complication of tonsillitis. Tetanus results in muscular spasms and prolonged muscle contractions throughout the body, including the jaw, and is caused by an infection of a bacterium called Clostridium tetani.


Any restriction or inability of a person to open his or her mouth can be referred to as trismus. Severe cases are often referred to as lockjaw. There are many possible causes, including trauma and various infections and diseases that affect the mouth or jaw area. Disorders of the central nervous system also might cause a person to become unable to open his or her mouth normally. Dental surgeries, such as a molar extraction, can cause inflammation that also might result in lockjaw.


One of the symptoms of tetanus is a tightening of the jaw muscles. This can gradually cause the jaw to become difficult to manipulate, affecting speech and swallowing. Untreated, tetanus can cause death, although this has become fairly infrequent because of vaccinations and the practice of re-inoculating people who have gotten cuts from dirty metal objects.

Tetanus is caused by a bacteria called Clostridium tetani. This disease was once thought to be caused by cuts obtained around horses, which are frequent victims of tetanus. Clostridium tetani, however, lives abundantly in soil all over the world. It can survive for about 40 years.

Incidence of tetanus is most frequent in third-world countries where inoculations are not routine. In fact, newborns make up about half the cases in countries that are unable to adhere to modern standards of cleanliness or where many people cannot afford the cost of vaccination. The leading cause of exposure to tetanus in these countries is the lack of proper care of the umbilical cord stump, which then becomes infected with Clostridium tetani.

When untreated, tetanus has death rates of about 30 percent for adults and 60 percent for infants. It is so deadly because the causal bacterium is a neurotoxin. As the disease progress, all of the facial muscles can become stiffened, causing lockjaw.

The sufferer's back, stomach and lower body might also be affected, creating a stiff but still painful paralysis. A side effect of the illness is violent seizures or muscle spasms, called tetany. The disease is extremely painful, particularly for victims who are experiencing tetany.

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Tricia Christensen
By Tricia Christensen
With a Literature degree from Sonoma State University and years of experience as a The Health Board contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.
Discussion Comments
By anon990034 — On Apr 02, 2015

I got tetanus from a Sanofy Pasteur Td injection. I woke up that night with excruciating cramps in both legs. I couldn't walk. The cramps lasted for hours, and I finally had to drag myself to a hot bath for some relief. It took ages to get better, and I had a red, spotty rash on body for months afterward. I posted it on the federal complaints website, and wrote to the company. Do you think they cared? No, they had already gotten the money for the injection. Do not get a Sanory Pasteur, supposedly preventive inoculation. It will give you tetanus!

By anon988632 — On Feb 12, 2015

I have just recently started experiencing a pain in my jaw and my ear. I am 35 and it is hard for me to chew. I am shrugging it off as maybe sinuses but there are times it is painful! Today it was so bad I did not finish my meal. What should I do or does anyone know a cause of this?

By anon359850 — On Dec 21, 2013

I suddenly experienced it, but only for a few seconds and then I just forced myself to close my mouth and I heard a sound that so scary. Thanks be to God, I closed it.

By anon312337 — On Jan 07, 2013

I agree with anon 133978 (post 6).You can ask an adult to do the same thing at home and it will help!

By Fa5t3r — On Nov 02, 2012

@pastanaga - People don't realize how delicate the jaw muscles can be, I guess. They get used so much every day, it's little wonder they go wrong sometimes.

I have never had any kind of lockjaw disease, but I've had severe muscle cramps in other areas because of overwork and I can definitely see how that might happen. Muscle inflammation is so painful.

The best treatment is to go to the doctor, rule out any other lockjaw causes, and if it's just muscle inflammation, to rest the area as much as possible, perhaps with a bit of gentle exercise as well.

I'm sure it's scary, but generally, as long as your tetanus shots are up to date, I don't think lockjaw is ever going to be life threatening, it's just inconvenient for a while.

By pastanaga — On Nov 01, 2012

Generally, if you have tetanus, you know it. It's not a gentle disease that only makes it so that you can't open your mouth. The muscle spasms aren't only limited to your jaw and they can be violent enough to break bones.

If you just can't open your jaw and the muscles around it are sore, it's probably some other condition. Lockjaw symptoms cover a wide range of conditions, most of which seem to be simply a problem with the muscles of the jaw.

By anon265774 — On May 03, 2012

So scary. I think I am suffering from the symptoms of lockjaw because I can hear that popping sound near my ear and when I yawn I find difficult to close my mouth, it is so painful. I'm afraid that I can't open my mouth due to lockjaw.

By anon224125 — On Oct 21, 2011

Yesterday I was rushed to the hospital because of this. I am so worried because it could cause death. What is the best medicine or treatment for this?

By anon215609 — On Sep 18, 2011

I had experience it twice. At first, way back, fourteen years ago, when I was yawning, suddenly locked my jaw for almost a minute. Then last night when I was yawning, again it locked my jaw for six seconds. what is the best medicine to cure it? I'm afraid it will trigger again.

By anon166348 — On Apr 08, 2011

I experienced this couple of years ago until now, and have just been ignoring it. I never thought that this could be a serious problem.

By anon137117 — On Dec 26, 2010

A few days ago, my left jaw locked. I could hardly close my mouth. After that, I started working my jaws up and down. I hear a loud popping sound on my left jaw. I continue working my jaw until the sound was almost gone. I was told to chew on my right side.

What to do about lockjaw? I'm afraid that this will happen again. Also, does hurting feet have any connection with lockjaw?

By anon133978 — On Dec 13, 2010

Last night i had my jaw locked accidentally because of yawning. I could not shut my mouth and it was too painful. I rushed to the hospital for first aid. the doctor put her thumb inside my mouth and pressed my lower jaw hardly then it was fine.

The doctor told me it might happen again because my jaw has lost its flexibility so anytime i feel like yawning i will massage my jaw till it pass. Thank god i can close my mouth again, but the pain is still there. -lady

By anon89538 — On Jun 10, 2010

My daughter got it and it lasted two days but I can't think of anything that could have caused it after reading that article. Although I agree with Katin: my daughter does talk a lot for a 19 year old.

By anon77031 — On Apr 13, 2010

I'm disappointed. what about the old words of wisdom: "lockjaw is caused by an anaerobic bacterium...that's why you should be careful about stepping on a rusty nail."

Was my mother so very wrong?

By katin — On Sep 01, 2009

Bacterium, huh, who would have thought?. And I thought it was caused by something else, like keeping your mouth opened for long periods of time. Remember your mom telling you to close your mouth or you'll get lockjaw? I won't have to listen now. Can lockjaw be caused by a severe blow to the head or injury? I never imagined this being a serious problem.

Tricia Christensen
Tricia Christensen
With a Literature degree from Sonoma State University and years of experience as a The Health Board contributor, Tricia...
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