JBJS Editor’s Choice—How Important Is the Knee’s ALL?

I think it’s safe to say that the anterior cruciate ligament (ACL) is the most-studied anatomic structure in the musculoskeletal system.  Yet more than a century ago, French surgeon Paul Segond identified a lesser structure in the knee, the anterolateral ligament (ALL), presuming it to be an important stabilizer of that joint. More recent research has associated this ligament with the anterolateral joint line capsular avulsion fragments associated with some ACL ruptures.

A “fashionable” interest in the ALL has re-emerged in that cyclic way orthopaedic surgical techniques and indications are prone to. Some surgeons are designing reconstruction procedures in which the ALL is addressed in addition to the ACL. While this may be a currently “fashionable” approach, carefully collected data presented in the June 1, 2016 issue of The Journal by Thein et al. clarify the biomechanical role of this ligament and suggest that ALL reconstruction is usually unnecessary. Using cadaveric knees and a robot instrumented with a universal force-moment sensor (see photo above), the authors carefully quantify the displacements that result from disruption of the ALL, as well as the load borne by the ligament both when the ACL is intact and disrupted.

Thein et al. conclude that while the ALL “may bear load in the setting of failed ACL reconstruction or chronic complete tears of the ACL,” the ALL carries minimal load in the ACL-intact knee—and that the need for ALL reconstruction “in a well-functioning ACL-reconstructed knee appears to be limited.” This well-conducted piece of research should restrain some of the enthusiasm for including the ALL when reconstructing an ACL-injured knee.

Marc Swiontkowski, MD

JBJS Editor-in-Chief