every once in a while i will get these knots on my legs, only a couple of times a year, but this time i had one come up on my foot and it looked just like i had broken my foot. it swelled up and turned all bruised and it hurt to walk on it. But it wasn't always sore, anyways i went to the dr this time and of course by the time i was going to the dr it was nearly gone but i went anyways he looked at it and then told me it was erythema nodosum. He said that it'll show up sometimes and then go away just like it has and that it was usually caused by something else stressful to the body, like cf. My question is does anyone else have this, or have any idea what it is?