Hi, I just had to join this site to respond. We just had to put our Belgian Sheepdog chow mix to sleep last week and are still grieving. She lived 18 years and had the same rear leg arthritic problems so when she was about 16+ we started carting her around in a double baby cart. I would love to know more about your dog and see if your dog was similair to ours (Cynder). I only have seen one other with this mix and I believe that dog was about 15+.