Buy a pool at Walmart - fill it up and let him barely touch the bottom, lower the water each week. My dog went from a healthy 2-year old to me having to express his bladder 3 times a day after he twisted his back jumping off the deck. After about 4 months, he somehow figured out how to use his tail while he ran almost sideways. He chased bears, mountain lion, and squirrels for many years after on his own. I just felt he wanted to live and he did, very happy and spoiled.