A hairline fracture (a crack in a bone so thin that it appears to be the size of a hair on an x-ray) hurts because the injury cracks through the periosteum (the outer layer of the bone) where the highest presence of nerve fibers exist with the bone, and therefore senses the most pain. read more
Hairline fractures, also called as stress fractures, are now slowly becoming an infamous dilemma in the area of sports medicine. Caused by application of repetitive strain and excessive training, hairline fractures are minute cracks on the bones, which can become severe if not immediately treated. read more
hairline fractures, compared to other forms of fracture, are the least painful. but, seeing as you got one in the face, that would hurt A LOT i would guess. i got a hairline fracture in the growth plate in my right thumb playing goalie and i barely felt it, just heard a pop. but i also have a high pain tolerance. read more