Trismus, also known as LOCKJAW, is a condition characterized by difficulty in opening the mouth due to muscle spasms. It is often caused by TETANUS, an infection caused by the bacterium Clostridium tetani. TETANUS is a serious and potentially fatal disease that affects the nervous system and can cause severe muscle spasms. Trismus can also be caused by other conditions such as temporomandibular joint disorder, stroke, or trauma. Treatment for trismus includes physical therapy, medications, and surgery.