I have a cousin who can pop his shoulders in and out just by trying. This can't be normal. Is it
eople who can dislocate their shoulders by will or on command often have abnormally loose shoulder ligaments or shoulder capsule. The shoulder capsule is a watertight sac that surrounds the joint. It is formed by a group of ligaments that connect the humerus to the glenoid. These ligaments are the main source of stability for the shoulder. They help hold the shoulder in place and keep it from dislocating.
Sometimes this type of shoulder instability is the result of trauma, injury, or repetitive load on the soft tissue structures. The result may be unidirectional or multidirectional instability. A unidirectional instability means the shoulder has too much movement in one direction only. Multidirectional instability refers to a shoulder joint that has too much movement or laxity in several different directions at the same time.
Someone who can voluntarily dislocate both shoulders at the same time most likely has multidirectional laxity caused by generalized ligamentous laxity. Another possible cause of this type of instability is a disorder of the collagen fibers that make up the soft tissues. One example of this pathologic condition is called Ehlers-Danlos syndrome (there are other less common collagen disorders).
Your cousin should be encouraged to see an orthopedic surgeon for evaluation and identification of this problem. Most likely he will be encouraged to stop dislocating the joints as this can cause microtrauma each time it happens. Avoiding future problems from chronic dislocations is important. Treatment to strengthen the muscles around the shoulder may be recommended to help prevent further injury.
Aaron J. Bois, MD, MSc, FRCSC, and Michael A. Wirth, MD. Revision Open Capsular Shift for Atraumatic and Multidirectional Instability of the Shoulder. In The Journal of Bone and Joint Surgery. April 2012. Vol. 94A. No. 8. Pp. 749-756.
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