However, when I try to do the short arc and long arc quad exercises, it is painful after the first 10 or 15 degrees of movement. I can DO the exercise and can extend to almost completely straight, but it hurts and my knee will get really irritated. I think if you were going to put these in a category you could say that anything that involves kicking out my foot when my foot is in the air/unsupported is a problem. But if my foot is on the floor, mat, pedal, etc. I can extend, flex, slide, push, whatever. My PT is stumped and I don't know what to tell him.