'Dem Bones, 'Dem Bones, 'Dem Bruised Bones
Ligament injuries in the knee often have an effect on other parts of the knee. Upon impact, the surfaces of the knee joint may slam into one another, bruising the bones. These bruises are actually tiny fractures of the bone underneath the cartilage. X-rays don't often show the bruises on the bone, but MRI scans can.
Researchers in Argentina set out to discover whether a bruised knee bone results in ongoing problems in the knee joint. They did an MRI scan on patients scheduled for surgery to repair a torn anterior cruciate ligament (ACL) in the knee. Participants were included in the study if this was their first knee injury and the MRI showed a bone bruise. Twenty-one people with a total of 29 bruises were found. The bruises were graded based on severity: type I being the mildest and type III being the most severe.
Within two to three years after surgery, another MRI was done. Most (91 percent) of the milder bruises disappeared completely. Yet none of the type III bruises went away. Even though the bruising appeared to resolve, this did not mean the bone had healed. In fact, the follow-up MRI scan showed that one-third of the patients still had an indentation in the bone where the bruise occurred. Others showed thinning in the cartilage of the knee joint.
Do these findings matter? Scientists believe they do. The concern is that the initial bone injury eventually causes the bone to become less resilient--less "bouncy." With the shock absorbers down, the cartilage that covers the knee joint takes more force. So even though the ligament has been successfully reconstructed, the hardening in the bone may lead to arthritic changes in the knee joint.
The researchers concluded that it isn't possible to predict long-term bone damage by whether or not the bone bruising has gone away.
References: Matias Costa-Paz, MD, et al. Magnetic Resonance Imaging Follow-up Study of Bone Bruises Associated with Anterior Cruciate Ligament Ruptures. In Arthroscopy. May/June 2001. Vol. 17. No. 5. Pp. 445-4.
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