I am having this same issue with Cadence where sometimes the back leg will give out now. Also she will sometimes have to sit down when climbing the stairs, although she gets right back up and keeps going. I have noticed it over time since we got her baby brother and it has become more pronounced this last month. I am proud of her that she still seems to want to behave like other quad paws, but sometimes tripawds "whoop it up" too much and end up hurting backs or straining muscles and knees. My fear is that she will seriously hurt herself "sidestepping" Einstein or hopping over him and twisting, (This dog can turn on a dime) which is what she seems to do the most. She is starting to let him know when it is getting to much, but I think I am going to have to control it more. They love playing with each other and she loves running, so it is hard to keep them apart. What people should know is that puppies can be too much, even for the healed tripawd. 

I was reading some of the rehabilitation stuff on this site and I am interested in it. I would even like to take some classes and learn to do it on Cadence myself. The problem is, is that the ones I have researched require you to be a vet or have some other type of certification. There seems to be nothing for the lay person. I do massage her but I think she needs more core building stuff. Her appetite is great and I think with her high protein diet she will develop strength and muscles quickly. I just need to know how to get started. 

Cadence's Mom