The Temporomandibular Joints are where the lower jaw attaches to the skull. These are a complex system of bone, muscle, ligaments and tissue. So really TMJ is the name. The actual prognosis is TMD or Temporomandibular Joint Disorder.
Most common is with TMJ is when the articular disc is displaced causing the jawbone and the temporal bone to make contact. It is very painful. Sometimes click or pop sound can be heard when moving the jaw.