The patella (from the Latin, meaning “little plate”), also known as the kneecap, is a small, triangular-shaped, sesamoid bone located within the tendon of the quadriceps femoris, a group of muscles that straighten the knee. The patella protects the knee and gives leverage to the muscles. One of the most common running-related injuries, runner’s knee, is essentially an irritation of the cartilage of the kneecap. Normal tracking (gliding) of the kneecap does not occur, since the patella tracks laterally instead of up and down. The increased pressure of abnormal tracking causes pain in this injury.