by Cassandra DenHartog

This is always a difficult question, due to numerous problems that could happen and the fact that the shoulder is made up of several boney, muscular, and ligamentous structures. Let’s start off with a little anatomy review.

The shoulder is made up of three large muscles collectively called the deltoids, 4 rotator cuff muscles, and several other muscles.
The deltoids individually are the anterior deltoid, medial deltoid, and posterior deltoid. These muscles help the arm with flexion (moving forward), abduction (taking the arm away from the body), and extension (bringing the arm back behind the body).

Four muscles together make up the rotator cuff.This is commonly, incorrectly, called the rotatorcup or rotary cup. The rotator cuff is made up ofthe supraspinatus, infraspinatus, teres minor, and subscapularis. Together they stabilize the shoulder, hold the head of the humerus into the glenoid cavity, and maintain the shoulder joint.

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