More on the ALL ligament

Last week, I wrote about the discovery of a new ligament in the knee, the Anterolateral ligament (ALL).  This week I'm going to share my opinion on the ligament.  The first thing I thought when I read this, was "how did they just now discover this ligament?"  Doctors and scientists have been examining the human body, especially cadavers, for hundreds of years.  How could they just now discover a new ligament in the knee?  I'm not sure exactly what the answer to this question is.  Back in the late 1800s there was mention of this ligament, but nothing else came about until recently.  It could be that the location of the ligament made it difficult to find when examining the knee, or maybe it was mistaken for another structure.

Another important question is what is the clinical implication of this ligament?  Since it is on the anterior and lateral part of the knee, it would play a role in stabilizing the knee against anterior shear force.  An excessive amount of anterior shear force is a main mechanism for an ACL tear.  The ALL ligament might also be torn by this mechanism of injury, and since doctor's weren't aware of it's existence, it was not being repaired along with the ACL.  Thus, a person who sustained a tear of both the ACL and the ALL was only having one of the ligaments repaired, and therefore their knee was still somewhat unstable after surgery.  This is just a hypothesis, and much research and testing needs to be conducted to determine the exact clinical significance of the ALL ligament.