Iliotibial band

The iliotibial band is a thick band of fibrous tissue that runs down the outside of the leg. It begins at the hip and extends to the outer side of the tibia just below the knee joint. The band functions in coordination with several of the thigh muscles to provide stability to the outside of the knee joint.

If it becomes too short, the band rubs too tightly on the bone of your leg and becomes irritated. The tightness is usually the result of too much strain from overtraining.