"TMJ" stands for temporamandibular joint, which is the joint that joins your lower jaw to your upper jaw. The pain that you are experiencing is from a syndrome called temporomandibular joint disorder, but this is usually referred to colloquially as "TMJ" even though that is actually the name of the joint!
TMJ disorder can occur from a number of causes, including trouble with imbalance in the bite and grinding of the teeth. Regardless of the cause, the end result is pain in the joint and trouble with opening the mouth fully and with chewing. The treatments for TMJ disorder are varied, usually beginning with stretching exercises, physical therapy, and pain medications and progressing to bite correction and dental splints. In more severe cases, surgery
may be required.
TMJ disorder and lock jaw are not the same thing. Lock jaw refers to infection with the tetanus bacteria. This is a rare but usually fatal condition in which the muscles seize up due to infection with the bacteria. Fortunately, lock jaw or tetanus is very rare these days because we are all vaccinated against the condition!
Please follow up with your doctor
to discuss your TMJ disorder.