ITBFS is a common condition that has the potential to develop in runners. It usually develops due to people not taking time to stretch and release their muscles and they become overly tight.
The ITB is the thick band of fascia that you can feel down the outside of your leg. It is an extension of the TFL (Tensor Fascia Latae) muscle, which is one of your hip flexor muscles. The ITB connects your pelvis to the outside of your knee. It holds your leg ridged when you place all your weight on one leg and assists in keeping your knee in a straight position when you walk or run.
Many runners find that they get pain on the upper outside part of the knee and will be unable to run due to this pain, but are potentially OK with other activities. A massage to release the tight TFL and other surrounding muscles will help you to resolve this problem, enabling you to run pain free.