Anatomy of the Shoulder
The shoulder joint is perhaps one of the most complex in the human body. This animation demonstrates how the various bones, muscles, bursas come together.
The shoulder comprises of bones, ligaments, tendons and muscles that connect the arm to the torso.
The three bones that make up the shoulder joint include the clavicle (collar bone), the scapula (the shoulder blade) and the humerus (the long bone of the arm).
The shoulder has two joints that work together to allow arm movement.
The acromion clavicular, the AC joint is a gliding joint that forms between the clavicle and the acromion. The acromion is the projection of the scapula. The AC joint gives us the ability to raise the arm above the head.
The glenohumeral joint or shoulder joint is a ball and socket type joint. The ball is the top rounded part of the humerus and the socket is the bowl-shaped part of the scapula called the glenoid into which the ball fit. This joint allows the arm to move in a circular rotation as well as towards and away from the body. The labrum is a piece of cartilage that cushions the humerus head in the glenoid. This cartilage also helps to stabilise the joint.
The rotator-cuff is a group of four muscles that hold the humerus into the scapular. The rotator cuff muscles stabilise the glenohumeral joint and help with the rotation of the arm.
Two sac-like structures called the bursa are also located in the shoulder. The bursa secretes a lubricating fluid that helps reduce friction between the moving parts of the joint.
Together all these structures form one of the most flexible joints in the body