Bone is made of different kinds of
tissue. The periosteum is a thin layer of tissue that covers most of a bone. Where
come together, there is usually a layer of cartilage at the edges. The bone here is
called subchondral bone. Deep inside the bone is an area called the medulla. It contains
the bone marrow and fibrous tissue called trabeculae.
With a bone fracture, all of the trabeculae in a region of bone have broken. But with
a bone bruise, an injury only damages some of these trabeculae. An injury might cause
blood to build up in the area beneath the periosteum. This causes a subperiosteal
hematoma, a type of bone bruise. An injury might also cause bleeding and swelling
in the area between your cartilage and the bone beneath it. This causes a subchondral
bone bruise. Or bleeding and swelling can occur in the medulla of your bone. This
is called an intraosseous bone bruise.