I don't know about training before surgery, but I know proper training after surgery really helps. Then I'm not talking about some exercises given to you by a physiotherapist, but pretty hardcore strength training with a knowledgeable personal trainer, even just a few weeks after surgery. If you have the time and money, that would be a worthwhile investment.
Whoaw, slow down.
TS, I've just been through ACL surgery myself and am now 5 months into the recovery. I am also studying to be a PT.
Increasing, or maintaining, leg strenght is important before surgery. You should stick to what you PT tells you and perhaps to the exercises you are already comfortable with. Remember, technique, form and control will mean everything in the next few months. Two primary concerns going into and after ACL recontruction is the hamstrings and the vastus medialis(part of the quadriceps). The hamstrings hold your shin in place, which is a common problem with ACL injuries and the medialis/quadriceps let's you extend your knee, which can become an issue after surgery.
More importantly, what you do after the surgery matters a great deal. You will probably get some BW exercises, like knee extensions on the floor, ab/adductor, hip, hamstring and glute workouts. At first they will seem ridiculously easy, but as you will soon experience, hardly being able to bend your knee or straightening it, or walking even, will let you appreciate the difficulty.
Don't overdo it and don't bend your knee more than the allowed range, but don't slack off either. Follow the programs and do the work everyday, even if it takes time. At all costs, listen to your PT. Have patience, the strenght will come back.
For all that is holy, do NOT go crazy with "hardcore" exercises a few weeks after getting surgery(especially if it's reconstruction). It will jack up your knee even more. The recovery stage is important for your future. Remember, control and discipline.
Good luck!
