Inflammation of the Ilotibial Band causes pain on the outer side of the knee and possible hip pain as well.
The iliotibial band (IT band) is a thick band of fibers that begins at the iliac crest in the pelvis and runs on the outside of the thigh until it attaches into the tibia (shinbone). The gluteal or buttock muscle fibers and the tensor fascia latae (muscles of the hip joint) attach to it, and the band acts to coordinate muscle function and stabilize the knee during running.
When the band becomes irritated, friction may occur with walking or running, causing knee pain due to inflammation on the lateral part of the knee joint.
Foam roller stretch: Prop yourself up with one elbow and position the foam roller just under your hip. Move your body forward so that the roller works itself down the outer side of your thigh; stop when you get to your knee and then reverse the direction back to your hip. Roll slowly and when you find a tight spot pause and hold that spot applying a bit of tension.
Second stretch. In this position, gently press your knee away (towards your opposite foot) and grab your shin and pull it towards you