We went through this last year with our Rottie. I did a lot of research and there are 3 methods to help with a torn ACL. You first have to understand that once the ACL is torn it is not going to repair itself. New scar tissue is going to have to form to hold the knee together. Once the original ACL is torn there is no way to recover it. Vets often make you think that the ACL is actually getting repaired, it is not, new scar tissue forms to hold the knee in place.
In order of cheapest to most expensive the fixes are; extreme movement restrictions, "traditional" surgery, TPOL surgery.
The first method you pretty much keep the dog in a cage so it doesn't move around too much. When it needs to go to the bathroom you use a sling to help carry the dog. This can go on for months before you see improvement. You also have to be vary carefult that the dog does not run or jump as this can reverse all healing progress up to that point.
With the third method the knee is modified to form a "new" joint. This method is the most costly (up to $2,000) and requires specially trained vets. If you do a search online a lot of people believe this method can cause more harm then good. It seems a lot of vets are pushing it now a days though.
We went with the second option of traditional surgery. This runs between $700 and $1000 dollars and most vets can do it. It required an overnight stay at the vet.It involves drilling holes in the knee bones and using surgical thread to hold the bones together in the same way the ACL does. Eventually these threads will break but it all goes well new tissue should be in place before that time. We kept the dog in his kennel for about a month to let the knee heal and begin to form new tissue. I put his cage in the living room and only let him out to go to the bathroom. I fed him lots of bones and treats and we eventually got through it.
Our dogs surgery was about 9 months ago. Currently he is about 85% on the leg. He runs/walks fine. Every once in a while it gets a little sore and he favors it for a day or so but besides that I am happy with the route we took. I also give him glucosomine/chondriton supplements daily.
I highly suggest pet insurance if you plan on paying for procedures like these. Our same dog had an emergency spleenectimy a few months before his ACL. All in all we paid over $3500 for both surgeries since we did not have insurance. When you are faced with the decision of paying for surgery to save your pet's life you make it makes the decision much harder. In reality when I had to make these decisions money was not a factor. One downfall with pet insurance is that they don't cover ACL related issues for 1 year after the start of the policy.
If you have any questions let me know and I would be glad to help.