Diseases and ConditionsCommon Disorders of the Spine, Shoulder,
and Pelvis Glossary - Spine, Shoulder, and Pelvis Disorders
Dislocation of the shoulder means the displacement of the upper
arm bone (humerus) out of the shoulder joint. The shoulder joint
is the most frequently dislocated major joint of the body--often
caused by a significant force that separates the shoulder
joint's ball (the top rounded portion of the upper arm bone, or
humerus) away from the joint's socket (glenoid). The shoulder
can dislocate in several ways, including the following: Forward
and downward dislocation. These are the most common types of
dislocations, which are usually the result of falling on an
outstretched hand or on the shoulder itself. Backward
dislocation. This type of dislocation may be caused by a direct
blow to the front of the shoulder, or the violent twisting of
the upper arm. In addition, a shoulder can be partially
dislocated (the head of the upper arm is partially out of the
shoulder socket) or completely dislocat