For those too lazy.
" The periosteum is a thin layer of tissue that covers most of a bone. Where bones 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. It's also called a microfracture. 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 happen in the medulla of your bone. This is called an interosseous bone bruise.
The term bone bruise is fairly new. This is because healthcare providers only started diagnosing the injury when the use of magnetic resonance imaging (MRI) became more common in recent years. A bone bruise doesn't show up on an X-ray."
"Treatment for a bone bruise may include:
Resting the bone or joint
Applying ice to the area several times a day
Raising the injury above the level of your heart to reduce swelling
Medicine to reduce pain and swelling
Wearing a brace or other device to limit movement, if needed
Most bone bruises slowly heal over 1 to 2 months. A larger bone bruise may take longer to heal. You may not be able to return to sports activities for weeks or months."
--University of Rochester Medical Center