What’s a bone bruise and how significant is it? We’ve got a 15-year-old soccer player (our son) on the bench with an ACL tear and bone bruise and he’s not happy about it.

Now that we have technology like magnetic resonance imaging (MRI), we know that bones can be bruised. What does it look like on the MRI? MRIs are made of signals that show up as an image on the computer screen. The signals have various levels of intensity from light to dark. Changes in the signal pattern alert the radiologist to any problems.

In the case of bone bruises, blood pooling, fluid build up (swelling), and increased blood flow to the area show up on the MRI. Water that moves seen within the bone marrow (center of the bone) is another sign of bone bruising. If the injury is severe enough, there can even be tiny fracture lines in the bone referred to as microfractures.

Bone bruises of the knee from trauma in athletes affect the subchondral bone. This is the first layer of bone underneath the cartilage of the knee. The most common injury associated with bone bruising is a rupture of the anterior cruciate ligament (ACL). In fact, 80 per cent of all patients who suffer an ACL rupture also have evidence of bone bruising on MRIs.

Repeat MRIs show that the bruising goes away over time (usually within 60 days). Studies done so far don’t show any problem with returning to normal function after a bone bruise. Most athletes are back on the field within six months’ time.

The real question on everyone’s minds is whether or not the bruising will result in arthritis later. We simply don’t know yet. Long-term research is needed to follow athletes with bone bruising over a period of years to determine what happens and just how significant these injuries can be.