The Anterolateral Ligament & the Lateral Meniscus’ Synergistic Contribution to Rotational Knee Stability
Authors: Corbo Gillian Gabriela , Lording Tim , Burkhart Timothy , Johnson Marjorie , Getgood Al 
Published: November 2023

IntroductionThe anterolateral ligament (ALL) is an extra‐capsular structure running from the lateral femoral epicondyle to the lateral aspect of the tibia and lateral meniscus. ALL injury has been reported to contribute to high‐grade anterolateral laxity following anterior cruciate ligament (ACL) injury. Failure to address ALL injury has been suggested as a cause of persistent rotational laxity following ACL reconstruction. Due to the ALL's anatomic connection to the lateral meniscus, recent evidence also suggests that the ALL can be divided into two parts: supra‐ & infra‐meniscal. In addition to ALL tears, lateral meniscus posterior root (LMPR) tears have been shown to cause increased internal rotation and anterior translation of the knee. The literature has yet to examine the ALL in conjunction with the LMPR, therefore the objective of this study was to determine the role of the ALL & LMPR in controlling anterolateral rotational laxity in an ACL deficient knee.Methods16 fresh frozen cadaveric knee specimens (mid –femur to mid‐tibia) were potted into a hip simulator (femur) and a six degree‐of‐freedom load cell (tibia). Optical trackers inserted into the bone tracked the motion of the tibia with respect to the femur. Biomechanical testing involved applying a 5Nm internal rotation moment to the tibia while the knee was in full extension and tested sequentially in the following three conditions: i) ACLintact; ii) Partial ACL injury (ACLant) –anteromedial bundle sectioned; iii) Full ACL injury (ACLfull). The specimens were then randomized to either have the ALL sectioned first (ALLsec) followed by the LMPRsec or vice versa. Internal rotation and anterior translation of the tibia with respect to the femur were calculated. A mixed two‐way (3 serial sectioning conditions by 2 ALL section orders) repeated measures ANOVA (α = 0.05) was performed.ResultsCompared to the ACLintact condition, internal rotation was found to be 1.78° (p=0.026), 3.74° (p=0.001), and 3.84° (p=0.001) greater following ACLfull, LMPRsec and ALLsec respectively. LMPRsec and ALLsec resulted in approximately 2° of additional internal rotation (p=0.044 and p=0.010, respectively) compared with the ACL deficient knee (ACLfull). No difference was observed between the ALL and LMPR sectioned states or whether the ALL was sectioned before or after the LMPR (p=0.160). A trend of increasing anterior translation was observed when the 5Nm internal rotation moment was applied up until the ACL was fully sectioned; however, these differences were not significant (p=0.070).DiscussionThe ALL and LMPR appear to have a synergistic relationship with the ACL in controlling anterolateral rotational laxity. High‐grade anterolateral laxity following ACL injury may be attributed to injuries of the ALL and/or the LMPR. During ACL reconstruction, the posterior roots of both menisci should be inspected carefully to rule out concomitant injury, and if found, should be addressed surgically to aid in stability. Future testing is aimed at determining the tensile properties of the supra‐ & infra‐meniscal parts of the ALL to better understand the capacity they have to control rotation of the knee.Support or Funding InformationNSERC & CIHR