The sternoclavicular joint is the articulation of the sternum (breastbone) and the clavicle in the upper chest area.  Because this joint moves with almost every motion of the shoulder, it is a very frequently used articulation.  Although sternoclavicular syndrome is an uncommon cause of pain in the chest and shoulder, it can be confused with many other problems including disease of the shoulder joint, cervical spine disease or even the pain of a heart attack.  The joint may become injured during trauma, such as a car accident, overuse or subject to autoimmune diseases such as rheumatoid arthritis or ankylosing spondylitis.  The pain of sternoclavicular arthritis originates around the joint.  There is pain upon movement of the shoulder.  The joint may be swollen and tender to touch.  X-rays are useful to exclude fractures and other bony abnormalities.  Blood work is used to look for infection and autoimmune disease.  A bone scan and MRI may also be useful to look for pathology in the sternoclavicular joint as well as to exclude other causes of chest wall and shoulder pain.  The treatment of sternoclavicular syndrome is conservative and begins with non-steroidal anti-inflammatory medications, heat, ice, splinting and physical therapy.  Resistant cases may require injection of the joint with a local anesthetic and a steroid.