Post ACL Treatment

I had full ACL reconstruction 2 and a half weeks ago. I am now fully weight bearing and can almost straighten my leg again. However for some reason my operated knee still continues to give way? Was this not the purpose of an ACL operation. As you can imagine I am deeply concerned about this matter as I am a keen sportsman and can only describe any further problems with this knee as extremely depressing. If anyone can help me out with this matter I would be extremely grateful. Previous forums I have posted on have all instructed me to consult my Doctor, this however is easier said than done as the doctors who have overseen this operation seem to be impossible to contact and when finally reached simply talk over you and avoid the question.