The Anterolateral Complex: More than Just One Ligament ….

Just when you thought it was getting boring in anterior cruciate ligament (ACL) surgery (particularly since the double bundle vs. single bundle debate went quiet), enter the anterolateral ligament (ALL). It has been quite some time since we have seen such controversy in sports knee surgery. The 2013 publication by Claes et al1 opened up somewhat of a “Pandora’s box,” with many differing opinions being voiced in journals, meetings, and the popular press.2,3

Multiple debates and editorial commentaries have ensued, with many authors disregarding the existence of the ALL,3 some questioning its significance4 and many questioning its function5 and the best way to address its deficiency.5–7

However, similar to the double bundle controversy in the early 2000s,8 following which we were all directed toward a greater understanding of ACL anatomy, the ALL debate has refocused our attention away from the central pivot of the knee, toward the extra-articular and intra-articular secondary stabilizers of anterolateral rotation.

A recent consensus meeting highlighted just how far we have come since 2013.9 Multiple prominent investigators gathered with the aim of providing a summary of the historical and current knowledge, to agree on consistent nomenclature and to direct future research.

Agreement was reached that the ALL does indeed exist as a structure within the anterolateral capsule of the knee. We were also able to agree that a number of structures within the anterolateral aspect of the knee are important in controlling anterolateral rotation; namely the iliotibial band and the Kaplan fiber system, the lateral meniscus, as well as the ALL and anterolateral capsule. This is what we now refer to as the “anterolateral complex” I (ALC).10

It is clear from multiple biomechanical studies that high grade anterolateral rotatory laxity is not just an isolated ACL injury.4,5,11,12 Moreover, there is involvement from the structures of the ALC as well as meniscal lesions such as the medial meniscotibial injury (RAMP lesion).13 However, major questions still remain including: (1) Will an isolated ACL reconstruction suffice? (2) If not, what are the ideal indications to add an anterolateral procedure? (3) What is the significance of over-constraint? (4) Does graft choice make a difference? These questions and more, still need to be answered and will occupy our thoughts and research time for years to come.

Until then, it is vitally important that the results of recent studies are translated into the clinical domain. As such, it is my pleasure to act as guest editor for this issue of Techniques in Orthopedics, in which we have invited many of those aforementioned prominent investigators, to provide a synopsis of the relevant literature pertaining to anatomy, imaging, biomechanics, and clinical aspects of the anterolateral complex. I hope that the information will help provide readers with a greater understanding of the current knowledge, and stimulate further thought into future research studies. This way we can ultimately aim to refocus our attention back on our primary goal. That is to improve the outcomes for our patients following ACL injury.