I have been on Dialysis since June, 2011. (female, 55 years old, 5'11" 185 lbs) Last test showed kidneys functioning at 4%. I have noticed most of the long time patients have huge, round protrusions (knots) about the size of a ping-pong ball on their arms. I find that very disturbing. I developed a swollen, hard, area two weeks ago that is still tender , after an infiltration. What causes the "knots" I have seen and is there any way to prevent them.