luck, knees and anatomy

Monday, May 20, 2013

The consequences of an injury seem to be a matter of luck. It’s still early, but Eric Staal of the Carolina Hurricanes may have dodged a knee catastrophe by “only” tearing his medical collateral ligament (MCL) while playing in the World Hockey Championships in Sweden. It seems that the other three ligaments that hold his knee together were not damaged and if his luck holds, he will not need surgery. His hockey career will be able to resume by the time training camps open in the fall.

A ligament is a thick band of tissue that spans across a joint and helps hold it stable, preventing movement in a direction the joint isn’t supposed to go. The knee is a hinge joint and there are four ligaments that keep it moving in the proper direction and not wobbling about. The medial collateral (MCL) and lateral collateral ligament (LCL) prevent sideways motion, while the anterior (ACL) and posterior cruciate ligaments (PCL) prevent back and forth sliding. When the knee works well, the quads in the front of the thigh and the hamstrings in back, allow flexion and extension for walking, running, squatting and jumping.

Sprains talk about ligament damage. A first degree sprain describes ligament fibers that are stretched but not torn. When the ligament is partially torn, it is classified as having a second degree sprain. Tear the ligament completely and it’s a third degree sprain.

Mr. Staal suffered a third degree MCL sprain and yet he has a lucky injury. The injury mechanism involves force applied to the outside of the knee causing it to buckle. Usually there is torque applied and the anterior cruciate ligament is torn at the same time. ACL sprains usually require surgery and a year’s worth of rehab and recovery. Adrian Peterson’s quick return to the NFL is not considered the norm. Add damage to the medial meniscus, the cartilage within the knee joint, and you have O’Donoghue’s terrible triad, in the 1950s a devastating career ending injury. (New surgical techniques may have removed terrible from the description, but it’s still a big deal). An isolated third degree MCL sprain, without other knee damage occurs less than 20% of the time and instead of immediate surgery, the knee is allowed to heal itself.

The ligament needs time so that collagen fibers, the building blocks of many of the soft tissues of the body, can bridge the gap between the torn ends and allow the body to reconstruct the ligament. Usually, the knee is checked every 7 -10 days to get a sense of whether the ligament is tightening up and after a month, a decision can be made whether the pace of non-surgical healing is adequate. The key, though, is to be certain that other ligaments are not involved.

Once upon a time, one of the orthopedic surgeon’s great skills was physical exam, trying to decipher the subtleties of ligament damage, in the face of swelling and pain. Was the knee stable because the ligaments were intact or were the quads and hamstrings protecting the knee, preventing a proper diagnosis? Technology has overshadowed physical exam skills, with MRI being the gold standard to look at joints, cartilage, ligaments and muscle. However, the MRI is not perfect and hands-on exam still has relevance. An MRI cannot tell how loose a ligament or how weak a muscle.

One would think that the anatomy of the knee would no longer be a mystery but it seems that new discoveries continue to be made and the function of ligaments still retain a little mystery. There are two layers to the medical collateral ligament, and within the superficial MCL are fibers that have a special purpose and renamed the posterior oblique ligament (POL). Not unique and yet not completely separate from the MCL, this ligament helps with stabilizing the knee when it is fully extended and acting as a dynamic stabilizer to  the knee as it flexes. Luck holds for Mr. Staal. The POL fibers may have been spared major damage.

Once upon a time in the history of medicine, the subjects of anatomy and physiology were thought to be dead ends. Once the material was mastered, there was nothing new to learn. With new ways of peering into the body, the surface of understanding body structure and how it functions has just been scratched. Even the presumably uncomplicated knee continues to reveal little mysteries about how it works and how it can recover from injury. A generation or two ago, there would be no MRI for Mr. Staal and he might have had to face surgery to not only fix the injury but also to make the diagnosis. Another stroke of luck that he got hurt in the 21st century and perhaps dodged an operation so that nature could take its course.

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