Temporomandibular joint (TMJ) disorders can cause severe pain or discomfort in your jaw joints (temporomandibular joint or TMJ) and supporting muscles. TMJ disorders (temporomandibular joint dysfunction or TMD) can also lead to headaches, earaches, or the inability to fully open or close your mouth (lockjaw). Chronic pain in your jaw bones or muscles are usually best addressed by a dentist. However, lockjaw can be a medical emergency that requires immediate attention, as it can begin to have serious effects on your health very quickly. It is also a common symptom of tetanus, which can threaten breathing and lead to death.