When an artery or vein in an extremity is damaged by a blow or a fractured bone and there is no open wound that will allow the blood to escape, the blood from the damaged blood vessel is trapped in the surrounding tissues.

Since the marrow in the center of bones like the femur produces blood cells, a fracture can result in significant internal bleeding even if no major blood vessels are damaged.

a. Internal bleeding into the tissues of the arm or leg can result in hypovolemic shock due to blood loss. Signs and symptoms of hypovolemic shock are given in paragraph 7-2.

b. Other signs of internal bleeding in an extremity include discolored tissue (bruises) and swelling of the injured limb. Swelling can be identified by comparing the circumference of the injured limb to the circumference of the same area on the uninjured limb.