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The shoulder is a ball-and-socket joint that has three main bones: the humerus (long arm bone), the clavicle (collarbone), and the scapula (also known as the shoulder blade). These bones are cushioned by a layer of cartilage. There are two main joints. The acromioclavicular joint is between the highest part of the scapula and the clavicle. The glenohumeral joint is made up of the top, ball-shaped part of the humerus bone and the outer edge of the scapula. This joint is also known as the shoulder joint.
The shoulder joint is the most mobile joint in the body. It moves the shoulder forward and backward. It also allows the arm to move in a circular motion, and to move up and away from the body.
Shoulders get their range of motion from the rotator cuff. The rotator cuff is made up of four tendons. Tendons are the tissues that connect muscles to bone. It may be painful or difficult to lift your arm over your head if the tendons or bones around the rotator cuff are damaged or swollen.
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