Author: Courtney Misher, MPH, BS R.T.(T)
Last Reviewed: October 13, 2022

Trismus, also called lockjaw, is when you have a hard time opening your mouth. It can also change how you look. Trismus may make it hard for you to:

  • Eat.
  • Swallow.
  • Speak.
  • Performing mouth care.

What causes trismus?

Cancers of the head and neck can cause trismus, or it can be a side effect of your cancer treatment. Trismus can also be caused by trauma, inflammation, surgery, or infection. Trismus may develop due to cancer because there is:

  • A tumor in your jaw.
  • Nerve damage from surgery that was done to remove your tumor.
  • Scar tissue from your radiation treatment.

Radiation is the most common cause of cancer-related trismus. When trismus is caused by radiation, it is usually associated with other side effects as well. These side effects may include xerostomia (dry mouth), mucositis, and pain. Other side effects associated with trismus include pain in the ear and jaw, headaches, and trouble hearing.

Your chance of having trismus is related to the amount of radiation your jaw got during treatment. The more radiation your jaw got the higher your chances are that you will have trismus.

How is trismus diagnosed?

Trismus develops slowly and often gets worse as time goes by. Your provider can take a series of measurements to see how wide your mouth will open and if it is getting better or worse.

One way to self-monitor for trismus is the 3-finger test. Holding 3 fingers together, try to insert them vertically between the top and bottom teeth. If they cannot fit, there is likely some restriction of the jaw. Let your provider know if you have any tightening in your jaw.

How is trismus prevented and managed?

Exercises to prevent trismus should start before treatment and continue forever. Treatment is most effective when started early. You will be taught how to do exercises that maintain maximum opening of the jaw. These exercises should be done 3-4 times a day. How wide you can open your jaw will be measured before, during, and after treatment.

Physical therapy may use multiple tongue depressors bound together or devices such as TheraBite® and Dynasplint to exercise and stretch the muscles to restore mobility and flexibility.

Medications such as pain relievers, muscle relaxants, and anti-inflammatories can be used to help manage trismus. A soft diet can also be helpful.

Trismus can greatly affect your daily life and the best course of action is to start exercises before trismus develops. Your care team will discuss if you are at risk for trismus, give you prevention exercises, help you to manage this side effect, and to help you to find out if your insurance will cover any treatment devices.


Cohen, E. E., LaMonte, S. J., Erb, N. L., Beckman, K. L., Sadeghi, N., Hutcheson, K. A., Stubblefield, M. D., Abbott, D. M., Fisher, P. S., Stein, K. D., Lyman, G. H., & Pratt-Chapman, M. L. (2016). American Cancer Society Head and Neck Cancer Survivorship Care Guideline. CA: a cancer journal for clinicians, 66(3), 203–239.

Trismus. The Oral Cancer Foundation. (n.d.). Retrieved October 5, 2022, from


December 20, 2023

Surprise! Financial Assistance To Help With Your Medical Bills May Be Available!

by Christina Bach, MSW, LCSW, OSW-C

July 19, 2022

Managing Side Effects with South Asian Foods

by OncoLink Team

June 2, 2022

Five Questions With…Gini.

by OncoLink Team