Fractures of bones are very common in connection with other accidents. Old people are especially liable to injuries of this kind on account of the increased proportion of earthy matter in the bones in old age. Fractures of long bones in children are very likely to be but partial, or what is known as "green-stick" fracture. Fractures may occur from a blow, fall, or violence of any kind applied directly to the limb, or may result from indirect violence, the bone being broken in consequence of a blow received upon some other part of the body, as in fracture of the collar-bone from a fall upon the hands, or the base of the skull from force received upon the top of the head. Bones are also sometimes broken in consequence of violent muscular action, as in fracture of the knee-pan which occasionally occurs in consequence of violent efforts in jumping.

Fractures are variously classified as complete or incomplete, transverse or oblique, crashed, impacted, simple or compound. Simple fracture is one in which the skin is not broken. In compound fracture the injury to the bone is accompanied by a lacerated wound of the part. This is a much more severe accident than simple fracture.

Fractures are indicated by pain, swelling, change in the form of the injured part, and a grating sound or crepitus felt by rubbing the ends of the fragments together. Loss of power of the voluntary motion in the limb, and an unnatural degree of mobility shown upon manipulation, are other characteristic signs. In examining limbs supposed to be fractured, they should be carefully compared with those of the opposite side.