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
Belgian doctors have identified a “new” knee ligament in humans, although a French surgeon speculated on its existence as far back as 1879. The anterolateral ligament or ALL, is a narrow band of tissue originating at the lateral femoral epicondyle and traveling obliquely to the anterolateral aspect of the proximal tibia. Researchers think the ALL functions to stabilize the outer part of the knee and prevent it from collapsing inward. When people tear their ACL doctors presume that the ALL is also torn, and that its rupture and subsequent withering may have contributed to its obscurity. There’s still a lot to learn about the ALL as surgeons are now in the initial stages of planning and practicing surgical procedures for treating all tears.