If your shoulder is wrenched upward and backward, you may dislocate it out of its socket. This condition is both painful and incapacitating. The force required is often that of a fall or a collision with another person or object (both of which can occur during many sports).

Most shoulder dislocations happen at the lower front of the shoulder, because of the particular anatomy of the shoulder joint. The bones of the shoulder are the socket of the shoulder blade (scapula) and the ball at the upper end of the arm bone (humerus). The socket on the shoulder blade is fairly shallow, but a lip or rim of cartilage makes it deeper. The joint is supported on all sides by ligaments called the joint capsule, and the whole thing is covered by the rotator cuff. The rotator cuff is made up of four tendons attached to muscles that start on the scapula and end on the upper humerus. They reinforce the shoulder joint from above, in front, and in back, which makes the weakest point in the rotator cuff in the lower front.

Subluxation refers to a partial dislocation. A subluxation occurs when the two joint (articular) surfaces have lost their usual contact. A 50% subluxation means the normally opposing articular surfaces have lost half their usual contact and the joint is partially dislocated. A 100% subluxation means the articular surfaces have lost all of their contact. A dislocation is the same as a 100% subluxation.

Shoulder Dislocation Symptoms

The main symptom of a shoulder dislocation is severe pain at the shoulder joint.

1.   The patient will have great difficulty moving your arm even a little bit.

2.   If the shoulder is touched from the side, it feels mushy, as if the underlying bone is gone (usually the humeral head – top of the arm bone – is displaced below and toward the front).

3.   A dislocated shoulder occurs when the humerus separates from the scapula at the glenohumeral joint. The shoulder joint has the greatest range of motion of any joint in the body and as a result is particularly susceptible to dislocation and subluxation. Approximately half of major joint dislocations seen in emergency departments are of the shoulder. Partial dislocation of the shoulder is referred to as subluxation.

TYPES

1.   Anterior (forward)   ::Over 95% of shoulder dislocation cases are anterior. Most anterior dislocations are    sub-coracoid. Sub-glenoid; subclavicular; and, very rarely, intrathoracic or retroperitoneal dislocations may occur.It can result in damage to the axillary artery.
2.   Posterior (backward) :: Posterior dislocations are occasionally due to electrocution or seizure and may be caused by strength imbalance of the rotator cuff muscles. Posterior dislocations often go unnoticed, especially in an elderly patient and in the unconscious trauma patient.An average interval of 1 year was discovered between injury and diagnosis of posterior dislocation in a series of 40 patients.
3.   Inferior (downward) :: Inferior dislocation is the least likely form, occurring in less than 1% of all shoulder dislocation cases. This condition is also called luxatio erecta because the arm appears to be permanently held upward or behind the head.[7] It is caused by a hyper abduction of the arm that forces the humeral head against the acromion. Inferior dislocations have a high complication rate as many vascular, neurological, tendon, and ligament injuries are likely to occur from this kind of dislocation.

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