The extensor digitorum muscle (also called the “extensor digitorum communis”) is one of the key muscles on the backside of the forearm. The extensor digitorum muscle helps in the movements of the wrists and the elbows. It also provides extension for fingers 2 through 5, as well as for the hand and wrist. The muscle originates from the lateral epicondyle, and then sub-divides down into four separate tendons. The tendons run through an enclosure of the lateral carpal ligament layered between a sheath of fibrous tissue. 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.