The ilio tibial (IT) band isn't a muscle; it's a thick strip of much less elastic tissue called fascia, a fibrous material similar to tendons and ligaments. The IT band begins on the outer hip and connects to the leg bones at the outer knee, and its primary function is to stabilize your knee. Most yoga teachers, myself included, think it's not a good idea to stretch fascia. These tissues receive much less blood than muscle does, which means that even small tears heal slowly and the scarring makes […]
2009, Danny Dreyer, Katherine Dreyer, ChiRunning: A Revolutionary Approach to Effortless, Injury-Free Running, Simon and Schuster (→ISBN), page 229
Often the pain may not appear until you are a mile or two into your workout, and may feel worse as you continue or when you run or walk downhill or downstairs. Many times the pain will subside if you stop running momentarily and walk with very short steps. That's because walking minimizes the rubbing of the band over the joint. Most often IT band problems occur at the knee, but you may also feel discomfort closer to your hip, and/or all along the IT band due to its tightness.