Lockjaw, which is also sometimes called trismus, is a condition in which a person’s jaw muscles spasm. If you develop lockjaw, your jaw may be “frozen” in a certain position, and you might not be able to open your mouth wide. Lockjaw can occur in association with a variety of health conditions, including cancer treatment, tetanus, and as a medication side effect.
Lockjaw can be painful, and it can cause complications, such as choking.1 Treatment includes oral (by mouth) or injected muscle relaxants. Sometimes, physical therapy is needed to help regain muscle control.