Trismus, also sometimes called lockjaw, is a painful condition in which the chewing muscles of the jaw become contracted and sometimes inflamed, preventing the mouth from fully opening. For most people, fully opening the mouth means opening it beyond 35 millimeters (mm) wide — a little greater than the width of two fingers.
When the mouth’s opening movement is restricted, a number of problems can arise. These include feeding and swallowing problems, oral hygiene issues, and even difficulty speaking. While trismus is not widespread in the population, it’s sometimes commonly seen in certain groups, particularly in those who:
- have had oral surgery to remove their wisdom teeth
- have had head and neck cancer in a region involving structures that influence mouth movement
- have undergone surgery or radiation treatment to the head and neck
Trismus is not the same condition as tetanus, which is also sometimes called lockjaw. Tetanus is an infection caused by the bacterium Clostridium tetani. Because there’s a vaccine for preventing tetanus, it’s a rare infection in the United States. However, when tetanus does occur, one will have muscle stiffness and spasms that are painful and could occur anywhere in the body. A notable area where this occurs is in the head and neck region, where it causes trismus.
Trismus can occur when there’s damage or injury to the muscles of the jaw. This can happen due to:
Examples of this include when bones of the jaw are fractured or when they’re immobilized to let a fracture heal.
While trismus can arise after any oral surgery, it’s sometimes seen after the extraction of wisdom teeth, especially the lower wisdom teeth. (Wisdom teeth are the last molars on each side of the jaw.) Trismus can occur due to the inflammation the surgery creates or the hyperextension of the jaw during the procedure. It can also happen when a needle delivering the anesthetic inadvertently damages surrounding tissue. Learn more about recovery after wisdom tooth removal.
Temporomandibular joint disorder (TMJD)
On each side of your jaw there’s a temporomandibular joint. This joint acts as a sliding hinge, connecting your jaw to your skull and allowing you to open and shut your mouth. When there’s dysfunction in the joint, it can cause trismus and pain. Joint dysfunction can happen due to:
- stress-related behaviors like the habitual clenching and grinding of teeth
Radiation for head and throat cancer
Tumors that interfere with the function of the jaw itself can lead to trismus. But it more commonly occurs due to radiation of cancer involving the jaw. This can cause damage and lead to the creation of scar tissue around the joint area.
The Oral Cancer Foundation states that 10 to 40 percent of those with head and neck cancer receiving radiation will develop trismus. Radiation that affects the temporomandibular joint, the pterygoid muscles, or masseter muscle (all of which play a major role in chewing) is most likely to cause trismus. The risk of trismus also seems to be dose related. A 2016 study noted that every 10-Gy increase in radiation (after an initial 40-Gy dose) to a pterygoid muscle ups the risk of trismus by 24 percent. Gy is a unit of measurement for radiation therapy.
A mouth that will not fully open — causing opening difficulty — is the hallmark of trismus. Other symptoms may include:
- pain in the jaw, even without movement
- difficulty or discomfort performing activities that involve opening the mouth wide (things like brushing your teeth or biting into an apple)
- inability to chew or swallow certain foods
- cramping in the jaw
Your doctor will first perform a thorough medical exam, specifically looking for signs of oral cancer, bone and joint abnormalities, or any other abnormal tissue in your jaw that may lead to trismus. They’ll also:
- measure how wide you can open your mouth
- ask about any recent dental treatments or procedures
- ask about any possible injuries to your jaw — for example, if you were hit in the jaw during a sporting or car accident
- ask about any history of prior surgery or radiation therapy to your head and neck
- order imaging studies such as a CT scan or an MRI scan to help determine whether your trismus is stemming from a problem with your joints or tissues
Trismus is more commonly temporary than permanent. But the earlier you start treatment, the better the chance for a greater recovery. Some treatment options include:
- Use of a jaw-stretching device. These devices fit between the upper and lower jaw. A physical therapist will tell you which stretches to perform and how often. Studies indicate the devices may help increase the mouth opening by 5 to 10 mm.
- Medication. Your doctor may recommend or prescribe a muscle relaxant, pain reliever, or anti-inflammatory medication. In one study, those who had the anti-inflammatories prednisolone (glucocorticosteroid) and diclofenac (nonsteroidal anti-inflammatory drug) injected intramuscularly after wisdom teeth extraction had less trismus than those given prednisolone alone.
- Physical therapy that involves massaging and jaw stretching.
- A change to a predominately soft-food diet until symptoms improve.
Together with medical intervention, there are things you can do at home to help relieve trismus and prevent it from worsening. You can try these two or three times during the day.
- Massage. Find the areas of your jaw that are painful and, moving your fingers in a circular motion, massage the area for about 30 seconds.
- Move your jaw left to right, hold for a few seconds, and then move it right to left.
- Move your jaw in a circular motion. Make 5 circles to the left, and 5 to the right.
- Open your mouth as wide as you comfortably can, holding this position to stretch it for a few seconds.
- Stretch your neck. Tuck your chin into your chest and hold for 30 seconds, then bring your head back and hold for another 30 seconds. Similarly, move your head to the left and then the right. Finally, move your head in a circular motion.
Avoid clenching your jaw shut or grinding your teeth together.
While trismus can be painful, it’s usually temporary and responds well to both medication and physical therapy. If you’re having dental surgery or radiation or surgery for head or neck cancer, talk to your doctor about ways to reduce your risk of developing the condition. The earlier you receive treatment, the better the outcome, so don’t hesitate to seek help right away if you notice any trismus symptoms.