Why does shoulder dislocation cause visible deformity after injury?

The shoulder is designed for movement: the rounded top of the upper arm sits against a shallow socket. During a dislocation, that relationship is lost, so the usual rounded contour may look flattened or squared. The arm may be held in an unusual position and movement can be severely restricted. Pain, swelling, guarding, tingling or weakness may occur because nearby muscles, nerves and blood vessels can also be affected. A visible change after trauma needs prompt medical assessment even if the pain begins to ease.

Keep the arm still in the position that feels most comfortable and support it with a sling or folded cloth if available. Apply a wrapped cold pack while arranging urgent medical care. Do not try to push the shoulder back into place, force movement, massage the joint, or eat and drink in case a procedure is needed. Remove rings or watches if swelling is developing.

Go to an emergency service promptly after a suspected dislocation or obvious deformity. Call emergency help if the hand becomes cold, pale or blue, if there is worsening numbness or weakness, uncontrolled pain, heavy bleeding, or a serious fall or collision. A clinician needs to check the joint and circulation and may use imaging before treatment.

Ask what structures were injured, how long the sling is needed, and when gentle movement should begin. Ask which positions to avoid, how recurrence risk will be reduced, and when rehabilitation can restore strength.