The shoulder joint consists of the head of the humerus and the joint socket. It is surrounded by a capsule, strengthening ligaments and muscles that contribute to the mobility of the joint. A shoulder instability can be caused by a natural disposition (e.g. with a capsule ligament deficiency) or it is the consequence of an injury. With the instability caused by an injury (shoulder
Luxation
) the so-called joint lip (
Labrum
), joint ligaments and capsule can be ruptured or a fracture of the joint socket or of the head of the humerus could have occured additionally. A shoulder instability causes repetitive painful dislocations of the head of the humerus out of its socket, e.g. after heavy falls, sports that involve upside-down postures or even after simple twisting movements. Sometimes the shoulder can only be reposed with help. Sometimes incomplete, painful "subluxations" can occur.