The iliotibial band is a large, thick, tendon-like band that starts at the outside of your hip and runs down to just below your knee. Your large buttock muscle and a smaller muscle of your hip both attach to this band and hold it stable. This band helps with certain movements of your thigh.

ITBS is an irritation of the iliotibial band usually around your knee. It is a syndrome that most commonly occurs in runners or cyclists. After a long distance run, you may notice a pain on the outside of your knee that can spread up or down the leg. If your ITBS is mild, the pain will leave shortly after you stop running. If your ITBS is more severe, the pain may last for the rest of the day and hurt during walking and stair climbing.