The acromioclavicular joint (AC Joint) lies between the end of the collar bone (clavicle) and the acromion (part of the shoulder blade). In women, this is near where a bra strap rests. The AC joint is stressed with overhead and cross arm movement. It lies immediately above the rotator cuff.

The rotator cuff is the anchor of the shoulder, responsible for the vast majority of motion and strength. It is comprised of 4 different tendons. A rotator cuff tear occurs when one or more tendons detach from the bony head of the humerus (upper arm bone). Most tears occur in the supraspinatus tendon, but the other three tendons (subscapularis, infraspinatus, teres minor) may be involved. There are two major types of tears and two major causes of tears.

The shoulder joint is made up of the humeral head (ball) and glenoid (socket). Even though it is referred to as a ball and socket joint, the anatomy of the joint is more like a golf ball on a golf tee. This shape allows the shoulder to move through a large arc of motion. To deepen the socket and prevent the shoulder from shifting, there is a structure called the labrum which surrounds the socket.

Biceps tendinitis is an inflammation or irritation of the upper biceps tendon. Also called the long head of the biceps tendon, this strong, cord-like structure connects the biceps muscle to the bones in the shoulder. Pain in the front of the shoulder and weakness are common symptoms of biceps tendinitis.