Your shoulder is made up of the upper arm bone, which is called the humerus, along with the shoulder blade, or scapula. The place where these two bones meet is called the "glenohumeral joint." This joint is surrounded by a joint capsule made of tough fibers. In normal conditions, most of your shoulder motion occurs at this joint.

Your shoulder joint is a ball and socket joint, where the top or head of the humerus is the ball and the shoulder blade provides the socket into which the ball fits. Your body works continuously to keep the ball in the center of the socket. This is analogous to a seal balancing a ball on its nose. That seal works quite hard at keeping his nose centered in the middle of the ball, keeping a delicate balance to assure that the ball does not fall off his nose.

In order to keep this balance of the ball on the socket, four muscles, known as the rotator cuff muscles, work to hold the ball securely in the shoulder joint socket. These four muscles attach to the humerus by the rotator cuff tendons, and they appear to surround the ball of the humerus like a glove. The rotator cuff muscles act dynamically in a delicate balance to keep the ball of your shoulder joint centered in the socket of your shoulder joint.


Shoulder problems are commonly caused by a breakdown of the soft shoulder tissues from participation in sports, overuse in daily activities and as we age. The most common shoulder injuries and conditions include dislocation, separation, and rotator cuff issues. To learn about some of the most common shoulder injuries and conditions, view the videos, below.

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