I've been raising several different breeds of rabbits (Mini Rex, American Sables, Cinnamons) in all-wire cages for a little over three years, and have had no problems with sore hocks or other cage-related injuries. The wire cages are easy to clean, durable, and safe--that is why I use them. All of the rabbit breeders I know (some who have been raising, breeding, and showing rabbits for decades) also use wire cages.
From what I've heard, the only time when solid-bottomed cages are a good idea is when raising "giant" breeds, like Checkered Giants or even Flemish Giants. Those larger breeds put so much pressure on their paws that sometimes wire isn't the best choice. Still, that can lead to sanitation difficulties, among other things, and there are certainly breeders who raise very large breeds on wire successfully.
Also, I don't deny that there are some breeds (like Mini Rex) that have strains which are more susceptible to sore hocks. This tends to be a genetic problem; fortunately, the Mini Rex that I am currently raising seem to be hardy, well-furred, and resistant to sores.
Edited by BantamLover21 - 12/13/16 at 3:38pm