A friend of mine tore his ACL about a year ago and is still suffering from the complications. I'm no doctor but from what I've heard and what a orthopedic surgeon told me, tearing(fully or partialy) your ACL is a giant pain in the butt with rehab, knee brace and surgery. Although a lot of times surgery is not always the better option, and some patients just have to accept dealing with a bum knee for the rest of their lives and a very long rehabilitation period. In most cases you're better off tearing your PCL which should give you an idea how much it sucks to tear an ACL.
