How much force does it take to break a bone?

We couldn’t find any clear answers to this question, because a lot of factors need to be taken into account. Even though according to The Handy Anatomy Answer Book by Patricia Barnes-Svarney and Thomas E. Svarney, one cubic inch of bone can theoretically withstand the weight of around five pickup trucks, and is ounce-for-ounce stronger than reinforced concrete, most of us know someone who has broken a bone, because bone will still break on impact. Charles Q. Choi, writing for LiveScience, says that this is because force is generally delivered quickly, and David Biello, writing for Scientific American, adds that the angle of the force affects whether the bone will break, and what kind of fracture it will be.

On UC Santa Barbara’s Science Line, the writers explain that bones are designed to withstand certain types of stress – arm and leg bones, for instance, have curves to them. This makes them able to resist force from certain directions, but vulnerable from the others.

According to DK’s Human Body, a transverse fracture, where the bone breaks straight across the width, is usually caused by a direct or angled force, whereas a comminuted fracture, where the bone breaks into several fragments, is caused by direct impact. A greenstick fracture, where a bone bends and cracks but does not break all the way across, is most common in children, whose bones are still relatively flexible. As we age, our bones become more porous and fragile, and fractures become more likely.