The extensor digitorum muscle is one of the main muscles on the backside of the forearm. It is found in human beings and other mammals, and is also sometimes known by the name of extensor digitorum communis. It provides an extension for the medial digits in the hands. The muscle originates from the lateral epicondyle, and then segregates down into four tendons. The tendons run through an enclosure of the lateral carpal ligament layered between a sheath of mucous. The four tendons eventually separate on the posterior part of the hand, and extend into the distal and middle finger phalanges. The tendons to the four fingers are interconnected with the help of two slanting bands. In some cases, the first and second tendons may be interconnected by a small transverse band. This group of bands is called the sagittal bands. Their function is to keep the extensor tendons aligned properly above the metacarpal head. This helps to improve the hand's leverage. The extensor digitorum muscle helps in the movements of the wrists and the elbows.