Lockjaw (trismus) happens when your jaw muscles tighten up so much that you can’t open your mouth properly. It's most often associated with tetanus, a dangerous infection from Clostridium tetani ...

TMJ disorder can cause intense pain in the jaw, neck, and head. If left untreated, TMJ disorders can lead to chronic pain, difficulty chewing, swelling, and in rare cases, it may lead to nerve damage.