
I don’t think that’s the case. Sometimes when they amputate a leg at the knee, they reattach the healthy foot onto the leg to act as a knee. It was actually discussed as an option for my half sister when she had her legs amputated but due to complications, she needed a higher amputation. The idea is to try to cap off the nerves as best as possible to minimise phantom pain and other discomforts (as far as I remember what the doctor said). When he fell, since the ankle is more prone to rolling over than a kneecap is, it rolled and dislocated. That’s what you’re looking at. Dislocation of a joint not a complete 180 of the joint. This is why his boots are so important. It’s partially a prosthetic.

Yes, because he injured it really badly because his shoe broke whilst he was running, causing it to fuck up his leg and he was freaking out.
The other commenter has it wrong. His leg was never amputated and he doesn't wear a prosthetic, he wears a fitted platform boot as his disability is that his legs arent in proportion to one another. Of which you can see in chapter one (his foot is the way it has been this whole comic, it literally shows him injuring it and getting it twisted due to trying to escape)

Whilst the other commenter is correct on how it works nowadays with some disabilities, this doesn't apply to his disability (which is that his leg didn't develop the same as his other one due to whatever reason that caused it) and what you see in these panels is him injuring it badly, and then the vampire taking pity on him and trying to heal it. (He’s still going to be disabled like before, just not with a twisted broken foot from trying to escape)
Tripping so hard that it changed his foot direction