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Stephania Bell on knee injuries

Posted by ESPN.com’s James Walker

With Pittsburgh Steelers Pro Bowl safety Troy Polamalu sidelined with a MCL sprain, a lot of AFC North fans are suddenly interested in how the knee heals.

  • Tim from Columbus, Ohio writes: Which is the more important knee ligament: ACL or MCL? And why does it take so long to heal when they are injured?

Because I didn’t go to medical school, I contacted ESPN medical expert Stephania Bell to answer this question.

Here was Bell’s response:

  • “Both ligaments are critical to the knee as they make up two of the four primary stabilizers of the joint. That being said, it’s almost impossible for most people to function when their ACL tears, and braces are not very effective in compensating for that injury, which results in front-to-back and rotational instability. So it tends to be the more devastating. An athlete with a torn MCL can function decently while it’s still healing with a brace, because the brace controls medial-lateral stability (MCL function) pretty well. A torn ACL won’t heal on its own, and it sits deep inside the joint and has to be reconstructed. The MCL, because it lies flat against the knee (it attaches the inner aspect of the thigh bone to the leg bone but sits OUTSIDE the actual knee joint), can repair itself by forming scar in the majority of cases. By keeping an athlete with an MCL tear in a brace initially, it helps the tissue to scar down. Ligaments in general don’t have the greatest blood supply which is why they often take a little longer to heal.”