With osteopetrosis, the legs should feel hard from what I have read. With gout or MS they would be swollen and soft. It's odd because the feet in your picture don't look swollen, so that is why I had mentioned osteopetrosis. With gout the feet would probably be swollen, they can be swollen with MS. I would read through the links to see if anything matches. MS is usually treated with Tylan or chlortetracycline, which won't cure it, but should help the symptoms. If a vet is available, they could be of more help. Testing can be done to determine MS easily.