Hello: I have a swelling in my left leg below the knee. The spot is about the size of my small finger. I did have a procedure Sept. 12th to remove or clear blockage in the anterior tibial artery, but the Cardiologist decided not to extend the catherator to the artery as the femoral artery was clean and suppling sufficient blood to my foot. Some light pain on the left side of lower leg. Ultra-sound did not find anything, like a blood clot. I can press on the spot and it feels like fluid, similar to a cyst? What is it?