What's happened to my foot?

Well, I was on the laptop laying on my bed and all of a sudden this sharp pain came, very very strong and I started crying because it was really bad and I lifted my leg up and it hurt even more. I tried to turn it and i couldn't because of the amount of pain this was causing me. The bone in my ankle felt loose and it felt like my foot was coming of. the pain ran all the way up my left leg and into my knee and now my whole leg is hurting. I can walk on it but I can't bend it or put it in certain positions, it is very painful, what's happened to it?