While not directly a shoulder problem, Sternoclavicular Joint Dislocation may affect shoulder functionality due to problems with sternoclavicular rotation. A sternoclavicular separation occurs when the sternum separates from the clavicle at the sternoclavicular joint.
Sternoclavicular separations (dislocation and subluxation) are rare and generally caused by accident. If the clavicle is separated posteriorly (i.e. the clavicle separates and goes behind the sternum) the situation can be dangerous and the clavicle can cause damage to interior arteries, veins or organs.
An X-ray or CT Scan may be necessary to accurately diagnose a sternoclavicular separation.