A shoulder dislocation occurs when the head of the humerus (upper arm bone) pops out of the shallow shoulder socket of the scapula (called the glenoid). This can happen when a strong force pulls the shoulder upward or outward, or from an extreme external rotation of the humerus.

Glenohumeral dislocations are generally classified by the direction of dislocation of the humerus.

Dislocation can be full or partial:

  • Partial dislocation (also called subluxation)—the head of the humerus slips out of the socket momentarily and then snaps back into place
  • Full dislocation—the head of the humerus comes completely out of the socket

Shoulder dislocations can also be associated with fractures—one can have a fracture and dislocation at the same time. Nerves and blood vessels can sometimes be injured with a severe shoulder dislocation, requiring immediate medical attention.

Shoulder Dislocation
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Shoulder dislocation can be caused by:

  • Falling on an outstretched arm
  • A direct blow to the shoulder area, such as in automobile accident
  • Forceful throwing, lifting, or hitting
  • Force applied to an outstretched arm, such as in a football tackle