Fractures most often happen when more force is applied to the bone than the bone can take. Bones are weakest when they are twisted.
Bone fractures can be caused by falls, injury, or as a result of a direct hit or kick to the body.
Overuse or repetitive motions can tire muscles and put more pressure on the bone. This causes stress fractures. This is more common in athletes and military recruits.
Fractures can also be caused by diseases that weaken the bone. This includes osteoporosis or cancer in the bones.