Temporomandibular (TM) disorders can result from a single cause or, more commonly, a combination of causes.

The main causes of TM disorders include:

• Muscle tension (tightness) and spasm. Muscle tension in the jaw, face, head, neck, and shoulders may make your jaw feel achy, stiff, and painful, especially when moving your jaw. Muscle tension may be:
  • Caused by stress and anxiety and by stress-related habits, such as daytime or nighttime clenching or grinding your teeth (bruxism), excessive gum chewing, or nail biting.
  • A response to structural problems within the joint or injury to the joint.
• Problems in the internal structure of the joint, such as:
  • Displacement of the disc that cushions the joint.
  • Degenerative disease, such as osteoarthritis or rheumatoid arthritis, which causes inflammation and destruction of the joint tissues.
  • Scar tissue or bone damage caused by accidental injury or a blow to the jaw.
  • Disease, such as a tumor, or structural problems present at birth (congenital).

In most cases, it is not possible to fully determine the causes of TM disorder symptoms.¹ In many cases, TM disorder symptoms appear to be caused by both muscle tension (tightness) and joint dysfunction. It is not always clear which came first. For example, osteoarthritis can cause changes in the joint, which may then bring on muscle spasms. Conversely, muscle spasms over time hinder jaw function and can eventually cause osteoarthritis in the jaw joint. A similar relationship appears to exist between muscle tension and disc displacement within the joint.

Orthodontic treatment and malocclusion do not trigger TM disorders or make them worse.

When jaw joint problems are caused by diseases such as rheumatoid arthritis, treatment for the underlying condition is important. Many other conditions cause symptoms similar to those of TM disorders, such as migraine headaches and infections.