Donald,
these days, we suggest using TPLO procedures to repair ACL tears on Rotties and other large dogs. We've found that the other, more conventional repairs, don't work as well or as long nor do they keep the incidence of arthritis down. At his weight, I would have thought that your orthopedic surgeon would have suggested it.

BTW, 173 is a very BIG GSD! Stop with the Miracle Grow! Getting his weight down would help but knee problems are not uncommon in breeds where we've bred in extreme rear angulation, especially GSDs. Rotties too. I speak as a person who has had 5 knee surgeries so I empathize.

Sorry to see him having to go through this. Good luck with the recovery. If you have a hydrotherapy center near you, I suggest you use it to strengthen the leg without putting any stress on the repair.

Jim