What is it?
The shoulder joint is the most commonly dislocated joint in the body. The shoulder joint is a ball-and-socket joint, and a dislocation occurs when the ball (which is the head of the humerus or arm bone) moves out of its normal position inside the shallow socket (which is the glenoid, a part of the shoulder blade). Typically, the ball moves in front and below the socket, but it can move behind the socket as well.

Causes
Shoulder dislocations usually occur when the arm is violently forced out and away from the body. Damage to the ligaments and bone often occur, which may lead to recurrent dislocations, especially in younger athletes. Less energy may be needed to cause repeat dislocations because of the damage from the original injury.

Risk Factors
• Young people participating in contact sports • Prior dislocation • Loose ligaments, or “joint laxity”

Symptoms
• Shoulder pain • Inability to move the arm normally • A feeling of the shoulder being out of place • Visible deformity of the shoulder joint

Diagnosis
Most patients with a shoulder dislocation show up with their arm held in a position of comfort. The shoulder joint usually has an obvious deformity. There will be tenderness around the joint with limited motion. X-rays can further help identify the underlying abnormality, particularly with respect to which direction the shoulder is dislocated, and if there is an associated fracture. Advanced imaging such as ultrasound, magnetic resonance imaging (MRI) and computed tomography (CT) scans can further assist with the evaluation of other structures in the shoulder.

Treatment
Immediate treatment of a dislocation involves relocating the ball into the socket as soon as possible. This can be done by a number of different techniques. Prompt relocation by a physician is preferred, and is easiest before the muscles go into spasm, which can make the reduction more difficult. After relocation, treatment may include a sling for comfort, ice, and pain management. A guided rehabilitation program is important for return of range of motion and strength. Braces can be used in some sports to decrease the risk of repeat dislocations. Surgery may be considered, particularly for younger patients, or for those who have dislocated more than once.

Prevention
Preventing future dislocations means fully rehabilitating the shoulder after injury. However, younger patients are still at very high risk for future dislocations despite adequate rehabilitation. This is why they may be referred for surgery even after their first dislocation, especially if they participate in sports or recreational physical activities.

Return to Play
Return to play is dictated by the return of full range of motion and strength without pain.

AMSSM Member Authors
Kyle Goerl, MD, Robert Dimeff, MD

References
Arliani GG, Astur DD, Cohen C, et al. Surgical versus nonsurgical treatment in first traumatic anterior dislocation of the shoulder in athletes. Open Access J Sports Med. 2011 Mar 15;2;19-24.

Cutts S, Prempeh M, Drew S. Anterior shoulder dislocation. Ann R Coll Surg Engl. 2009 January;91(1): 2–7.

Robinson CM, Dobson RJ. Anterior instability of the shoulder after trauma. J Bone Joint Sug Br. 2004 May;86)4_:469-79.