We have a 19 mo old black lab. Max had TPLO surgery in Oct and was diagnosed with osteosarcoma in that same leg in Dec, having amp surgery Dec 18. I know this is kind of reverse of what you are asking, but what I can tell you is how the recovery went for the TPLO. Typically, 8 solid weeks of rest and minimal movement is required for optimal healing. The dog is in pain quite a bit and has to learn to walk on the leg all over again due to the rebuilding and the healing of the bone(including a plate and screws to hold everyting in place). No stairs, no running, no jumping, a sling to help with stability. This may not be what your ortho vet plans on doing as far as repair surgery, however. Maybe there are other options? In my opinion, amp surgery recovery is much quicker than TPLO recovery, 2 weeks vs. 8 weeks.

 If you are considering amp and then cruciate ligament surgery, having been through both with my own dog, and at a younger age, I would not recommend it. That is putting your dog through weeks and weeks of recovery and pain at 12 years old. Only you as an owner can make a decision about what is best for your dog. I hope that I have given you some additional information that helps you make your decision. Hopefully its just arthritis! Best of luck to you! 

You are right about the weight being distributed to mostly the front legs, however, remember that in a tripawd you have to consider the balance factor. Many times they catch themselves with that back leg which puts more weight and stress on it.  I see Max do it all of the time. Just another thing to think about!

Best of luckto you!!! Im so glad that things worked out for the best (and they did!!) Remember that the first two weeks are TUFF! Rely on us to give you support and it will be over before you know it. Soon you will be wondering what you even worried about!