My small dog had both knees operated on before she was two years old. Over the years she would hold one leg up and hop on three. I was constantly saying “four legs, use all four legs.” She would put it down for about 2-3 steps and raise the other. I realized the other day I have not been saying “4 legs down” lately as she has used all her legs. She is 13 years old and has been on SierraSil for a couple of years now.