Our male North African/Greek cross tortoise is about 18 years old.  About 18 months ago his back legs seemed to become weak, but x-rays of the legs didn't reveal any obvious problems.  After hibernation last winter the problem seemed to have lessened and he had reasonable use of his back legs.  However, in the last couple of months he's lost all use of his back legs and his front legs seem to be weak as well.  His appetite is fine and he seems happy enough, although he can't get around at all now.  Any help would be very gratefully received.