A shoulder dislocation occurs when the head of the humerus (the ball of the upper arm bone) is completely forced out of the glenoid cavity (the shallow socket of the shoulder blade). This is the most frequent major joint dislocation in the human body due to the shoulder’s expansive range of motion. When the joint separates, the surrounding soft tissues, including ligaments, tendons, and muscles, are subjected to mechanical trauma. This injury requires immediate professional medical attention due to the high risk of associated complications.
Recognizable Signs and Symptoms
The onset of a shoulder dislocation is marked by immediate and severe pain localized at the joint. This pain often distinguishes the injury from a simple muscle strain or a lesser joint separation. Following the trauma, the arm is typically held in a fixed, slightly awkward position. Any attempt to move the joint actively or passively causes an acute spike in pain.
The most definitive way to recognize a dislocation is the visible change in the contour of the shoulder itself. The normal rounded curve of the deltoid muscle may flatten out or appear concave, sometimes creating a squared-off appearance beneath the acromion. The humeral head may also be palpable as a bulge in an abnormal location, which provides a physical confirmation of the joint’s displacement.
The separation of the joint components can lead to complications involving the adjacent nerves and vasculature. A sensation of tingling, numbness, or weakness radiating down the arm or into the hand suggests possible involvement of nerves, most commonly the axillary nerve. This nerve damage can result in sensory changes on the outside of the upper arm. Muscle spasms can also occur as the body attempts to protect the injured area.
Understanding Dislocation Types
Shoulder dislocations are categorized based on the direction in which the humeral head is displaced from the socket. The vast majority of shoulder dislocations, accounting for approximately 95 to 98 percent of cases, are classified as anterior dislocations.
Anterior dislocation occurs when the humerus head is displaced forward, often resulting from a fall onto an outstretched arm or a forceful blow to the posterior shoulder. Posterior dislocation is less common, accounting for only about 2 to 4 percent of cases, and involves the humerus head moving backward out of the socket. This type typically requires extreme force, such as that experienced during a seizure or an electrical shock.
A posterior dislocation can sometimes be missed on initial examination because the visual deformity may be less obvious than with an anterior displacement. Regardless of the type, the specific displacement helps medical staff anticipate potential associated injuries, such as fractures of the glenoid rim or damage to the rotator cuff. Imaging, such as X-rays, is necessary to confirm the direction of the dislocation and rule out any associated bone fractures before any treatment is attempted.
Immediate Actions and Warnings
Upon recognizing the signs of a possible dislocation, the immediate priority is to seek emergency medical care at a hospital emergency department. While awaiting professional help, the arm should be stabilized in the position it currently rests, using a makeshift sling or a pillow to support the arm against the body. Immobilizing the joint minimizes further damage to the surrounding soft tissues and nerves.
Applying a cold compress or ice pack, wrapped in a cloth, to the area can help manage swelling and pain, provided it does not require moving the joint. Neither the patient nor any untrained person should attempt to reduce the shoulder by forcing it back into place. Attempting self-reduction risks causing damage to the axillary artery or the axillary nerve, which can lead to permanent nerve or vascular injury.
Moving the joint without prior X-ray imaging can convert a simple soft-tissue injury into a complex one involving a fracture of the humerus or glenoid rim. Individuals should refrain from eating or drinking anything after the injury occurs. This is a standard precaution, as the medical team may need to administer general anesthesia or sedation to safely perform the joint reduction procedure.