What Causes Swollen And Painful Ankle?

The outside of my ankle is swollen up and hurts. My foot has been hurting if I stand up too long. If I stay off of it the pain subsides. I have had the sharp pain in it off and on for months, today is the first time I have had the swelling. No injuries and the pain seems to be going up my leg from my foot. Do you know what our be causing this?