(SPOILER) Overcoming his disability (SPOILER)

Just watched this yesterday and I enjoyed it. There was one thing, however, I thought was dumb; the killer's disability.

So he has one leg shorter than the other. That's fine. So he wears a special shoe. That's fine. Yet... he still limps? He shouldn't have limped, since he has a special shoe to fix his disability.

In fact, I'd say if he wore two regular shoes, he'd be fine.

Anyone else noticed this?

This is just my signature and is not part of the post lol...
- Signature, Mr