I'm in need of a knee cartilage graft from a car wreck, but now the back of my knee is puffy and swollen and has a bit of rash. Is it related to injy?

MVA knee pain. Most likely this is related. With regard to the surgery I would suggest that you speak to someone who deals in regenerative procedures (Stem Cell) in the knee. This may be a good option before any surgery - this also depends on your pathology also.