Improved technology in the area of advanced imaging such as magnetic resonance imaging (MRI) has made it possible to identify the extent of damage associated with anterior cruciate ligament (ACL) injuries. The location, depth, and intensity of bone bruising associated with ACL injuries are being studied more closely.
A classification scheme describing the depth of bone bruising is used to help guide the surgeon in making treatment plans. When the force of an injury is enough to rupture the ACL, the impact of the femur (thighbone) on the tibia (lower leg) is enough to leave a bruise called a footprint.
Superficial bone bruising means the footprint is seen beneath the subchondral bone. Subchondral refers to the layer of just below the cartilage of the joint. The deeper the bone bruising, the more damage has occurred in the nearby soft tissues such as the lateral or meniscal tears.
The long-term significance of bone bruising is unknown. Most of the time, the footprint is not seen on the MRI six weeks after the injury. There's evidence of chondral damage but no idea of the long-term consequences at this time.