Have had dogs in the house all our lives. Current one is on the way out. I can see it every day as it gets harder and harder for him to get up after laying down. We have always had large dogs and that is the way they come to the end of their lives. When they can't get down the stairs we can no longer care for them as neither my wife or me can carry them. The thing is that the large dogs suffering seems to be more of a psychological pain than physical. It must be very freighting to a dog to no longer be able to walk. What I'm trying to get around to saying is that I wouldn't make the decision to end a dog's life based entirely on pain. I had a pointer once who would run all day in sand burs if I would have let her. One time she ripped a toenail completely off and keep hunting like nothing was wrong. It's when the pain turns into fear that it is time to call it a game. I know that I have no particular fear of pain, it's being helpless that is frightening. That is not to say that pain cannot be debilitating but that is just another form of helplessness.