The iliotibial band is a wide strip of fibrous tissue that extends down the outside of the upper leg. Sources vary, defining the iliotibial band as a large tendon, a ligament, or an area of thickened fascia. The IT band begins at the top of the pelvis, at a boney prominence called the iliac crest, and travels down the outside of the thigh, continuing over the outside of the knee joint. The bottom of the IT band attaches to the top of the tibia (shinbone).