For a few days, I've had a strange throbbing sensation in the vicinity of my left knee. It feels vascular. It seems to be on the front side of the knee, which from what I understand is not typical of a popliteal aneurysm. It's not painful at all, but it is somewhat uncomfortable. Is it an aneurysm? Should I see a doctor immediately? What would the other signs of an aneurysm in this area be?