When you're noticing a tight IT band, you can often tell based on which parts of it are tight where the restrictions or instabilities are causing it. Typically, either the whole thing will be tight, or just the distal third. With the tightness of the distal third, I look at fibular restrictions or adhesions between the knee and the ITB. With tightness of the whole thing, I look at instability of the hip and/or ankle. You can also find local restrictions anywhere along its length (eg adhesion to the quadriceps) that will create tension in only that specific area.