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The joints and muscles of the elbow complex are designed to serve the hand. They provide mobility for the hand in space by shortening and lengthening the upper extremity, which allows the hand to be brought close to the face for eating and grooming or to be placed at a distance from the body equal to the length of the entire upper extremity. Rotation at the elbow complex provides additional mobility for the hand. In conjunction with providing mobility for the hand, the elbow complex structures also provide stability for skilled or forceful movements when performing manual activities with tools or implements. Many of the 15 muscles that cross the elbow complex also act at either the wrist or shoulder, thereby linking the elbow with function of the joints proximal and distal to the elbow.1
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The elbow complex includes the elbow joint (humeroulnar and humeroradial joints) and the proximal and distal radioulnar joints. The elbow joint is considered to be a compound joint that functions as a modified or loose hinge joint. The elbow joint has one degree of freedom, permitting the motions of flexion and extension in the sagittal plane around a coronal axis. A small amount of axial rotation and side-to-side motion (abduction/adduction) of the ulna occurs during flexion and extension, which is why the elbow is considered to be a modified or loose hinge joint rather than a pure hinge joint.2 Two major ligaments and five muscles are directly associated with the elbow joint. Three of the muscles are flexors that cross the anterior aspect of the joint. The other two muscles are extensors that cross the posterior aspect of the joint.
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