The iliotibial band is a thickened and strong tendinous strap which runs down the side of the thigh.
Function of the ITB
The ITB and the muscles associated with it function to extend, abduct, and laterally rotate the hip.
A Review of Treatments for Iliotibial Band Syndrome in the Athletic Population. Beals C and Flanigan D. J Sports Med (Hindawi Publ Corp). 2013; 2013: 367169.