http://www.sportsinjurybulletin.com/archive/acl-reconstruction.html
This implies that low to medium level strength training is what you want to do, and the sooner you can get up to 75% of the original strength level in the damaged leg, the sooner you can start to have “fun” again. Because most experts recommend against any kind of plyo until you have been strength training uninjured for a time, I would not be doing anything explosive like jump squats (which Charlie didn’t like even for healthy people) unless an expert approved.