Got a call from the surgeon this afternoon; the surgery went just fine, all is well, Ratty'll be home tomorrow or maybe the next day. He also said that it looked like an old injury, judging by the damage surrounding it.
Ratty's only seven months old. How old can an injury be?
I am still completely baffled as to how he did it in the first place, though I do recall that his feral mother gave birth to her kittens on top of a pile of wood under one of those little high-up windows in my downstairs garage. And I also remember scooping kittens up off the floor and returning them to her (as well as trying to make it safer by rearranging the boards so there was at least a little bit of a wall in the front).
He certainly hadn't been limping any earlier than the middle of last week.
I really don't know.