The elbow is so named because at this point the arm is usually bent. A joint is here inserted which permits of flexion and extension; when the arm is fully extended the " elbow" might be said to have disappeared. The lower end of the humerus forms the proximal portion of the joint and the upper ends of the ulna and radius form its distal portion. Ligaments join these bones together to form the joint, and the blood-vessels and nerves change in character in this region as they pass from the arm to the forearm.

The bones are frequently subject to fractures which are of an exceedingly puzzling and disabling character. The joint becomes luxated and the vessels and nerves are not infrequently injured. A thorough knowledge of the anatomy of the region is absolutely essential to the proper treatment of these affections.