Temporomandibular joint (TMJ) disorder is not a single condition but rather a group of symptoms that often include:

• Pain in the hinges that connect the lower jaw to the skull (temporomandibular joints)
• Headaches
• Earaches
• Limitations in jaw movement
• Clicking or popping sounds as the jaw moves
• Eye pain
• Neck pain, back pain or shoulder pain

Some estimates indicate that more than 10 million Americans suffer from TMJ disorder, according the National Institute of Dental and Craniofacial Research, part of the National Institutes of Health (NIH). This disorder is a complex and poorly understood group of conditions that can lead to pain in the jaw joints and surrounding muscles and other soft tissues.

TMJ disorder, also called TMD, is a common cause of orofacial pain. Patients often report pain while chewing as this disorder is often aggravated by movement of the jaw.

The muscles used during mastication (chewing) are part of the temporomandibular joints. A temporomandibular joint is located in front of each ear. Each temporomandibular joint connects the lower jawbone (mandible) to the skull. The bony surfaces of these joints are covered with cartilage and separated by small discs that prevent the bones from rubbing together. The temporomandibular joint is used for many functions, including biting, chewing, swallowing, speaking and facial expressions. TMJ disorder can thus affect a patient’s ability to speak, eat, swallow, chew and breathe.

Generally, the group of conditions known as TMJ disorder falls into three main categories:

• Myofascial pain, which includes pain related to the function of the jaw and may include the muscles of the neck and shoulders.
  
  
• Internal derangement of the joint, which includes either a dislocated jaw or a possible misalignment of the disc that provides a buffer between the skull and lower jaw.
  
  
• Arthritis, which can inflame the jaw joints. Several forms of arthritis can cause symptoms of TMJ disorder, including osteoarthritis (OA), rheumatoid arthritis, infectious arthritis, traumatic arthritis and gout.
  

The cause of TMJ disorder is unknown. However, researchers note that the majority of people affected are women in their childbearing years. Notably, many people with TMJ disorder also have other health concerns ranging from fibromyalgia and sleep disorders to irritable bowel syndrome and a heart condition called mitral valve prolapse. The relationships between these health concerns and TMJ disorder are not clearly understood and require further investigation.