Hi,
Bonnie must be so grateful to you for adopting her! It’s good that she’s in a nicer place now.
She may well have had sore hocks, or the start of them, when you got her. Once they start developing they can be difficult to stop. You’re doing good things in keeping her on blankets and changing the litter regularly. It’s also good that she’s a healthy weight.
My bunny has sore hocks despite my best husbandry efforts (probably the carpet just caused too much friction for her – she’s not a rex but does have unusual fur). I use a steroid cream on her hocks which keeps the inflammation down. She’s on blankets as much as possible now (she has free run of a room, in which I’ve covered the carpet with blankets, but sometimes she digs them up, and she also gets a run around the rest of the house a couple of times a day). I also cover over soiled litter on days that I’m not cleaning the trays out with a layer of fresh litter, just to help keep it dry. The vet doesn’t expect the fur on her hocks to regrow, though, so it’s a case of managing rather than curing.
Best wishes to you both!