The iliotibial band is the ligament that runs from the hip to the shin, on the outer side of the thigh. When functioning properly, the band is responsible for stabilizing and moving the knee. However, when the band becomes tight or inflamed as a result of overuse, it can no longer perform this function and, thus, any movement of the knee becomes painful (particularly on the outer side). This is what is referred to as iliotibial band syndrome. It is incredibly common in runners (more frequent in women), and in severe cases can keep a runner off the road for weeks. Wearing worn-out shoes, running on concrete, and racking up too many miles all can contribute the iliotibial band syndrome. Most people recover from iliotibial band syndrome with conservative treatment that includes plenty of rest and gentle exercises that stretch the band and strengthen the gluteus muscles. Some people may benefit from swimming, rowing, or other no- to low-impact exercises that don’t place pressure on the band. If symptoms persist, physical therapist-supervised heat therapy, electrical stimulation, and ultrasound also may be helpful. If pain persists, corticosteroid injections and surgery to release the iliotibial band may be last resorts.