Iliotibial, or IT, band syndrome is an injury that affects the tissues on the outer thigh and knee as a result of overuse of the tissues, according to MedicineNet. These tissues are collectively known as iliotibial band.
IT band syndrome commonly affects bicyclists and athletes, notes MedicineNet. One cause of IT band syndrome is anatomy defects such as leg-length discrepancy, abnormal pelvic tilt and bowed legs. These anatomy issues overtighten the iliotibial band, which eventually results in elevated friction during the band's back-and-forth movement across femoral epicondyle. Erroneous training may also cause IT band syndrome. For instance, athletes who run on roads that are higher at the center and lower on the edges may become affected by the road because the legs step on different ground levels.