Having been through an ACL reconstruction and a Meniscectomy, I feel your pain. After I damaged my knee it would literally lock in place sometimes and was unstable. I had a menicus tear that was causing the pain and locking up, the stability issues were from the ACL tear. It was definitely worth getting it all taken care of, much better after surgery!
My GUESS is that you have some cartilage that needs removed. Usually they do that with arthroscopic surgery and you will be down for couple of weeks or so. Good luck and hope the doc gets you fixed up.
