question: hi, out of the blue i had a burning aching sensation in my right knee. the patella was red and swollen with a swollen visible blue vein across it. it was hot to touch and tender. the swelling went down after about 10 min and the redness slowly disappeared. now a larger area over the patella is blue (on the right patella top left - if you were looking at my patella). it still hurts when i bend it as well. i have had tenderness in my right knee for a while that hurts when i do squats or sit at the desk all day with bent legs. any idea what it could be as i am really worried.