I have seen two bucks with swollen hooves like you described. One was shot by a neighbor, the other was being taken down by two big dogs in a creek. Where I live there aren't rattlers that we know of, and the one that was shot was in the winter, snow etc... The one being attacked was obviously impaired and that is how the dogs got on him. I surmise that they suffered some injury and infection set in. When they run out through the woods they are prone to break a leg on rocks and such.