Iliotibial tract. Computer artwork showing the muscle structure of the knee (top) and lower leg. Here the iliotibial tract (blue) is highlighted. The iliotibial tract, or iliotibial band, is a section of fibrous tissue (fascia) that lies over the muscles on the outer surface of the thigh, extending from the femur (thigh bone) to the tibia (shin bone). It acts almost like a ligament, helping to stabilize the knee joint, whilst also aiding in flexing (bending) and extending (straightening) the knee.