What is Lock Jaw and What Causes It?

What is Lock Jaw and What Causes It?

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH
Medical Reviewed on Feb 10, 2023
byDr. Matthew Hannan DDS
🔬 Evidence Based
What is Lock Jaw and What Causes It?

“What is lockjaw?” Depending on who you ask, lockjaw can either be specifically related to a tetanus (bacterial infection) from some type of injury or used as a general term describing a jaw disorder — such as TMJ issues. Lockjaw is also called “trismus”, which is when a person has limited movement in their TMJ, making it hard or impossible to open their mouth. Since lockjaw is used interchangeably with different types of conditions, knowing how to fix lockjaw first starts with a formal evaluation and diagnosis. Because if it’s caused by a tetanus infection in one person and a joint disorder in someone else, you’re going to need different types of treatment to get the lockjaw under control.

Common Lock Jaw Symptoms 

The most obvious symptom of lockjaw is not being able to open and close your mouth. Lockjaw makes it feel exactly like your TMJ is locked into place. Opening — even if just a small amount — is out of the question. Either your jaw physically won’t open or it’s extremely painful to do so.

However, if you have the “tetanus” version of lockjaw, you’ll also experience overall muscle stiffness throughout the body, headache, fever, changes in your heart rate and blood pressure, and seizures. Your entire body is impacted, not just your mouth and TMJ; but the lockjaw is one of the most obvious symptoms to watch for.

When trismus (lockjaw) is due to something functional — like trauma or inflammation in the jaw — it’s typically going to be a result of TMJ disorder (TMD). In those situations, how to fix lockjaw begins with managing your TMD. Symptoms frequently include popping and clicking in the joint, pain, headaches, earaches, and of course limited range of motion. You might also have misaligned teeth or undiagnosed sleep apnea.

If your lockjaw symptoms are isolated to your mouth, then it’s probably an orofunctional issue like TMD to blame. But if you’re experiencing co-existing physical symptoms in other parts of your body, and you know you were exposed via some type of injury (like stepping on a rusty nail) then it’s more than likely going to be associated with a tetanus infection.

What Causes Lock Jaw 

As a whole, lockjaw or trismus can be caused by several different factors. In years past it almost always meant you had a tetanus infection. But since the term is more generalized these days, it’s important to know which of the different causes could be playing a role in your discomfort. Some are life-threatening, others are not. Depending on how quickly the lockjaw condition comes on and what other symptoms you’re experiencing, you might be spot-on with your self-diagnosis.  

1) Tetanus

Tetanus is the original lockjaw. It’s typically caused by a form of physical injury such as stepping on a nail, contaminated wounds, or some type of puncture to the skin. When the Clostridium tetani spores (tetanus bacteria) enter your body, they can cause a toxic infection. Tetanus is life-threatening and has an incubation period of 3-21 days. In more aggressive wounds, the prognosis is poor.

2) Inflammation Of The Soft Tissue

Anything from a traumatic injury or infection to biting down the wrong way or overuse can cause temporary inflammation in the jaw. With swelling it’s common to see reduced range of motion (lockjaw) as well as discomfort from the inflammation. Pay attention to see if overuse is happening, such as eating firmer foods or chewing gum throughout the day. As with any joint in the body, constantly using one that’s sore can lead to additional swelling in the tissues around it.

3) Temporomandibular Joint (TMJ) Disorders (TMD)

TMD is what a lot of people think of these days when they’re talking about lock jaw. When your TMJ is sore, traumatized, overworked, dislocated, or not functioning correctly it will physically leave you unable to open your mouth all the way. Even if you can open just a small amount, your range of motion will be significantly limited. TMJ pain can also contribute to headaches, earaches, and atypical chewing patterns.

4) Infections

A lockjaw bacterial infection will probably be due to tetanus. But for the sake of conversation, let’s say that it’s not. Any infection in or near your jaw could potentially limit your range of motion. Perhaps you suffered an injury or had a medical or dental procedure performed that somehow became infected. That swelling could then radiate into the jaw muscles that move your mouth, preventing you from being able to open it all the way.

5) Medication

Researchers have found that certain types of antipsychotic medications have been linked to TMJ dislocations, causing lockjaw symptoms. It’s due to how the medications affect your dopamine and serotonin levels. Other prescription drugs that affect nervous tissues responsible for controlling muscle movement can also be possible causes. Reglan is another example, which is a medication that’s used for managing nausea and vomiting (typically following cancer treatments,) known to occasionally result in limited jaw movement.

6) Cancer

Deterioration of bone, soft tissues, or invasion of a tumor can physically alter your TMJ function. Cancer patients may even be given medications during their anticancer treatments that are linked to lockjaw (see above).

Complications From Lock Jaw

Worst case scenario, lockjaw can result in death. Particularly if it’s because of a tetanus infection. But if we’re talking about cases of lockjaw that are due to TMJ disorder, trauma, or infections, the complications are more uncomfortable than they are life-threatening.

Some of the most common non-tetanus lockjaw complications include:

  • Joint pain and jaw stiffness
  • Painful muscle contractions
  • TMJ dislocation
  • Limited diet
  • Inability to talk or smile normally
  • Pain on one or both sides of your mouth
  • Jaw deviation to one side
  • Irregular tooth wear
  • Broken dental work
  • Anxiety or depression

On the flip side, TMJ pain can also be a complication of another condition. For example, sleep apnea or bruxism. If you’re clenching and grinding your teeth together all night long, TMD can slowly begin to develop.

Diagnosing Lock Jaw

A physical examination with your dentist will determine if you have temporomandibular joint disorder or “lockjaw”. Usually, they will palpate (feel) your jaw joint as you open and close your mouth, observing irregularities such as the disc slipping out of place, popping, locking, or deviation to one side. In most cases, your dentist will also need to take a panoramic X-ray or full mouth 3D CT scan to assess the full anatomy of your TMJ and the structures around it. On rare occasions, an MRI may even be ordered at a medical facility. Especially if you’re in severe pain and unable to move your mouth hardly at all.

Tetanus-related lockjaw will of course, need to be diagnosed in a medical setting (usually a hospital, due to the severity of the condition.) Your physician will likely order blood tests and biopsies to determine if there is some sort of pathology playing a role. MRIs are also common.

How Do You Fix A Locked Jaw?

Fixing a locked jaw will of course depend on the precise cause behind it. Ideally, you’ll want to consider a non-invasive, non-surgical type of therapy that will physically help the TMJ function more freely without stiffness and discomfort.

Trying to figure out how to fix lockjaw without surgery? Here are some simple and effective tips approved by dentists:

  • Invest in a bite splint (occlusal guard)
  • Massage your TMJ and surrounding jaw muscles throughout the day
  • Alternate a warm and cold compress every 20 minutes
  • Consider getting braces to correct tooth misalignment
  • Get screened for sleep apnea
  • Exercise or meditate for stress relief
  • Take an over-the-counter anti-inflammatory (NSAID) such as ibuprofen as directed
  • Eliminate habits such as nail-biting or gum chewing
  • Temporarily switch to a soft diet

Long Term Treatment For Lockjaw

If you have lockjaw from tetanus, your physician will probably place you both in the hospital and on a strong regimen of medications. But assuming we’re talking about TMJ pain or TMD, it’s not going to be as much of an ordeal!

Your general dentist is the best place to start if you’re trying to figure out how to fix lockjaw associated with TMJ disorder. They can screen you for bruxism, sleep apnea, and atypical anatomy in or around your TMJ. Depending on the severity of your case, they can initiate treatment right then and there, or refer you to an oral surgeon for further evaluation.

Typical TMD-type treatments will involve things like:

  • Physical therapy to work on modified movement and range of motion.
  • Massage and moist heat, to loosen and ease tight jaw muscles.
  • Speech therapy or eating therapy if there are long-term side-effects that inhibit normal activities.
  • Injectables (such as Botox) to naturally relax the jaw muscles around your jaw and face.
  • Oral appliance therapy such as a mouthguard or bite splint to ease tension while sleeping or throughout the day.
  • Orthodontic treatment to correct malocclusion (crooked teeth) issues that contribute to oral function.
  • Surgical reconstruction or correction when there is damage to the internal disc or bone.

When To Talk To Your Dentist

First and foremost. If you have any reason to suspect that you’ve been infected with tetanus — such as from an open wound, puncture, muscle spasms, or a sore that’s not healing — seek out immediate medical attention before the symptoms become worse or life-threatening.  

On the other hand, if you have a variation of lockjaw or trismus that seems to be isolated to your TMJ, it’s best to go ahead and schedule an evaluation with your dentist. If you’re still able to eat with some modifications (such as pain relievers or cool compresses) you can schedule the appointment at your earliest convenience. Although most general dentists can help treat TMJ disorder, more aggressive cases of lockjaw may need to be seen by an oral surgeon for a consultation. You don’t necessarily need a referral if you feel inclined to go ahead and contact an oral surgeon directly.  

Fair warning: talking to an oral surgeon doesn’t necessarily mean you’ll need surgery, it just means you’ll have immediate access to an expert diagnosis and guidance on your particular jaw joint disorder.

Lock Jaw Overview

What is lockjaw? Depending on who you ask, they’ll say it’s a tetanus infection, trismus, or TMJ disorder. How to fix lockjaw begins with a specific diagnosis and whether or not there are co-existing medical symptoms. If your infection is because of a tetanus exposure, seek out immediate medical care. But if you’re certain that the joint pain is because of something going on with your TMJ, seek the advice of your dentist. 

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH"Teeth Talk Girl," is a registered dental hygienist. She started her dental health journey on YouTube, educating the public through videos.
Dr. Matthew  Hannan DDS
Medical Reviewed byDr. Matthew Hannan DDSDr. Matthew Hannan is a board-certified dentist and graduate of UT Health San Antonio School of Dentistry.
Last updated onAugust 17, 2023Here is our process

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