The IT Band injury puts a strain basically on the knee and the hip joints. It does not usually occur instantaneously but starts with a cramp or ache and rapidly goes on to become a debilitating sports injury, sidelining the best of runners.
The band is a thick tendon-like piece of another muscle which is called tensor fasciae latae which passes down the outside of the thigh and inserts just below the knee. If one observes the frontal view of the right thigh muscle, it can be seen that it runs right to the knee. This thick band is called the iliotibial band or iliobial track. When the tensor fasciae latae muscle and the band become stiff it results in knee pain or pain directly on the IT Band. The tension between them causes the tendon to displace the knee joint out of its position which causes irritation and swelling.
The causes of iliotibial band syndrome or ITB are mainly too much running when your body is unprepared and/or biomechanical errors. Overload is commonly associated with sports which involve loads of running as well as weight bearing activity which is basically why it is common in runners. The tensor fasciae latae muscles become fatigued and they cannot adequately support the entire leg. This subsequently puts pressure on the knee joint causing injury and ache.