The IT Band is not a muscle, but it sure causes a lot of pain. IT band aka Iliotibial band runs from our hip to just below the knee. It can cause lateral knee pain and lateral thigh pain, this condition is known as IT Band friction syndrome (from the IT band causing friction over the knee joint when it is overly tight). The IT Band is a large band of fascia and has many muscles pulling and innervating the fascia. One of the main muscles is TFL (tensor fascia lata), we also have gluteus maximus, quads (vastus lateralis) all pulling on the IT Band. So if any of these muscle groups are tight it is good to address them first then work on releasing the IT Band. Running, cycling, hiking or weight-lifting (especially squats) cause issues in the IT Band.
To stretch the IT Band you can do it in a standing position by crossing your legs and bending over to the opposite side of the back foot, hold for 30 seconds both sides. If on a sofa or bed it is a great stretch to be lying on your side with one leg in front. Have your hips and body at the edge of the bed, then allow the top leg to fall back slowly behind you and hold for 30 seconds. Use your upper arm to create balance.
Foam rolling is fantastic for this area, WARNING it hurts… a lot. But is effective in releasing the tissue. Be sure to roll out the quads, glutes and hamstrings as well.