What Causes Knot And Noticeable Vein On Kneecap?

I am worried abou deep vein thrombosis. I have a doc apt on Tuesday but worried about pulmonary embolism in the mean time. I had a little bad circulation feeling in my feet and hands. now I have a knot above my left kneecap and a noticeable vein about 2 inches long beside the knot. is that likely to be a blood clot. im a 28 year old female, not overweight , but not very active with no know health problems.