Bruising of the bone can have several meanings, types and origins. This is an injury that can occur from a variety of factors, including direct force trauma, sporting activities and injuries to our joints.
Bruising can occur within the bone marrow as well as outside it. It also can involve structures within the joints themselves.
A sub-periosteal hematoma is a collection of blood located underneath the protective membranous layer on bones called the periosteum. This occurs as a result of direct force trauma against a bone, typically in one of the lower extremities.
The periosteum is a thick, fibrous membrane that covers and helps nourish our bones. It is very vascular, meaning is has a large blood supply to it, so when there is a traumatic force applied to a bone, like jamming your shin on a coffee table, it can cause bleeding between the membrane and the bone.
These injuries are seen a bit more often in younger persons mainly because their periosteum is very thick, tough and less likely to tear as one would see in older folks.
Because there is very little space between these structures, there is little room for the blood to spread, so it forms a more localized lump under the periosteum that can take many weeks to months to resolve. This bump can also be quite sore to the touch.
Inter-osseus (which means inside the bone) bruising occurs from compressive forces being applied to a bone that cause internal injury to the bone marrow, typically from repetitive activities. Higher-level athletes are among those who are most affected by this injury type because of the extreme level of play and the intensity of the activities and training. Professional athletes, such as football and basketball players as well as runners, are at higher risk for these injuries.
When the bone marrow is injured, the blood supply within it is damaged, causing internal bleeding. This, in turn, can cause a buildup of pressure inside the bone, called bone marrow edema, which can cause pain and ultimately the death of the bone if bleeding and pressure are not resolved.
Typical areas for this injury type is in the knee and ankle because of the extreme pressure loads these joints endure on a regular basis.
A sub-chondral lesion is an injury that occurs beneath the cartilage layer of a joint. This can occur when the cartilage surface is damaged from causes such as direct and extreme compression or a shearing force applied to the cartilage that causes it to separate from the underlying bone.
Extreme compressive force injuries can include jumping and impact from running on hard surfaces.
The cartilage that covers our joints is very soft and plush and is susceptible to injury. During compression, the cells are literally crushed, and that energy can extend into the underlying bone, causing bleeding and a separation of the cartilage from the bone. These injuries are seen more frequently in football and basketball players.
Shearing force injuries are sustained from rotational mechanism, such as twisting, or translational forces (sliding of one of the bones in a joint, typically the knee, either forward or backward without restraint, as seen in anterior cruciate ligament injuries of the knee), which causes the cartilage tissue to be stripped away traumatically, exposing the underlying bone. In some instances, a small piece of the bone may accompany the cartilage as it is sheared away.