I had ACL reconstructive surgery in October 2008 and I have been having non-stop problems with my knee.?

I had a nerve block for my surgery and I even 6 months after my surgery I still couldn't feel parts of my leg. Almost 2 and a half years later I still cant feel parts of my leg. I also have a very hard lump under my knee cap. (a screw maybe?) It is only a few layers of skin to being completely exposed! I am also having a cracking and popping sound every time I move, also to top it off if I sit a certain way or cross my legs or anything my leg goes completely numb! Does anybody have any guesses to what might being going on?!?! Answers would be greatly appreciated!!! Please and thank you!