I blew my ACL out in Bosnia back in 97. Our good ole military docs kept saying it was only a sprain and kept sending my to physical therapy. well 6 months later I finally got the ortho doc to look at it and he blew a gasket wanting to know why I hadn't been to see him sooner. long story short He used the center section of my patella tendon to replace my ACL. my recovery went great and the therapy I did before the surgery got my knee strengthened up before hand.i think I was actually down for 4 weeks. It did take a long time though getting used to the gap in the front of my knee where they removed the tendon.