Iliotibal band syndrome otherwise known as IT band syndrome is the leading cause of lateral knee pain in runners. The IT band is a superficial tissue on the outer lateral side of the quadricep. 
The IT band is important for stabilization of the knee. The Iliotibial band gets inflamed by the constant rubbing over the femur. This can lead to these symptoms:
An irritation or pain on the outside of the leg just above the knee. This pain runs along the entire length of the IT band. This pain may worsen when your foot hits the ground from running.
Treatment:
Decrease your training distances, make sure you stretch before and after running, and ice the knee after activity. If you are suffering from pain try discontinuing activity until the pain goes away.
The IT band is important for stabilization of the knee. The Iliotibial band gets inflamed by the constant rubbing over the femur. This can lead to these symptoms:
An irritation or pain on the outside of the leg just above the knee. This pain runs along the entire length of the IT band. This pain may worsen when your foot hits the ground from running.
Treatment:
Decrease your training distances, make sure you stretch before and after running, and ice the knee after activity. If you are suffering from pain try discontinuing activity until the pain goes away.