about a year to a year and a half
one messenger here locally severed his ACL in december of 2005, he was back on his bike around july of 2006, and prettymuch back to normal by year end 2006, however, he will never ever be 100% again, just the way it is---------he switched to singlespeed for the most part, but does occasionally ride fixed, but he never has really ridden a whole lot, has like 4 customers and might ride 10-15 miles a day if that
doesnt mean eveyone is like that, but from what he told me it will never be 100% again, joint injuries, ligament tears or tendon injuries take a long time to get better, I know mine did when I had a distal radius fracture, that took more than a year to get better