You could accidentally hit your leg the wrong way and have a hair line fracture and never really think it is broken. It may hurt over a period of time, and unless you go to a doctor an have an xray you might never know it. A hairline fracture is still considered a break.
Falling down drunk - you won't feel a thing!
To just break it completely I would think because my brother fractures his ankle in three spots and the doctor told him he would have been better off to break it than fracture it.
Get yourself anesthetic and ask someone to chop it off!