Lockjaw disease or trismus refers to any condition with reduced ability to open the mouth. A person with lockjaw temporarily (in some cases, permanently) loses the ability to open and/or close the mouth. Some cases of lock jaw can cause extreme pain and discomfort. When left untreated, lock jaw can permanently impair the motor functions of the jaw, particularly when it comes to chewing or talking. The jaw joints play an important role in jaw movements. These are points of attachment of the lower jaw to the skull, one on each side of the face, just in front of the ears. Ligaments, tendons and muscles support the joint and are responsible for the various jaw movement. Jaw movement will be affected if any of these get injured.

Lockjaw can be caused by a number of factors:-

*Tetanus infections are common causes of lockjaw. Tetanus causes prolonged contraction of the skeletal muscle fibers and can lead to painful and violent spasms. One of the first signs of tetanus infections is lockjaw.

*Jaw dislocation – This happens when jaw joint moves too far forward and gets stuck in front of bony prominence. The surrounding muscle often goes into spasm and hold the jaw joint in a dislocated position.

*Inflammation of muscles and soft tissues around the jaws is the leading cause of lockjaw. Impacted wisdom tooth can cause the soft tissue surrounding the tooth to get inflammed. Infection originating from the lower back teeth can also cause inflammation of the surrounding tissue and abscess formation (accumulation of pus). This will lead to impaired function of the muscle that opens the jaw (muscle spasm)

*Limitations caused by factors internal to the joint include bony ankylosis (bone growth within the joint), fibrous ankylosis, arthritis, infections and trauma

*Side effects of some medications, particularly those used for psychiatric and mental disorders.

*Latrogenic causes e.g. complication of dental injection (when local anaesthetic is accidentally injected into the jaw muscle) and post-third molar extraction (in which the muscles of mastication may be torn, or the joint become hyperextended)