The Function of the Meniscofemoral Ligaments
Abstract & Commentary
Synopsis: The true function of the meniscofemoral ligaments remains unclear, but it may have profound implications for treatment of PCL-deficient knees and lateral meniscal tears.
Source: Gupte CM, et al. A review of the function and biomechanics of the meniscofemoral ligaments. Arthroscopy. 2003; 19(2):161-171.
Precise definition of the role of the meniscofemoral ligaments (MFLs) continues to be elusive. This article summarizes the available information about the MFLs by presenting a comprehensive review of the literature, beginning with the initial description of the ligaments by Humphrey in 1858 and suggests future studies to conclusively define their function.
The MFLs originate from the posterior horn of the lateral meniscus. The anterior meniscofemoral ligament (aMFL) of Humphrey passes anterior to the posterior cruciate ligament (PCL) to insert on the femur between the distal margin of the femoral attachment of the PCL and the edge of the condylar articular cartilage. The posterior meniscofemoral ligament (pMFL) of Wrisberg passes posterior to the PCL to insert at the proximal margin of the femoral attachment of the PCL.
The MFLs are variably present in each knee, and the incidence of the MFLs is the subject of many anatomical studies. Gupte and associates propose explanations as to why considerable variation of reported incidences exist, including variations in techniques of isolation of the ligaments, differences in criteria for defining an MFL, or even variability of incidence between races. An anterior dissection approach may underestimate the incidence of the pMFL, and misidentification of the oblique fibers of the PCL for fibers of the pMFL may result in an overestimation.
In an effort to elucidate the incidence of the MFLs, Gupte et al combine the results of the incidence data presented in the anatomical studies. This summary concludes that the overall incidence of at least 1 MFL is 91%. In the knees demonstrating at least 1 structure, the incidence of an aMFL is 48.2% and a pMFL is 70.4%. The incidence of both ligaments coexisting in 1 knee is 31.8%.
The general consensus is that the pMFL is a more substantial structure than the aMFL. The pMFL may be up to 50%, and the aMFL is often less than 33% of the PCL diameter. However, very little biomechanical research has been performed regarding the structural or material properties of the MFLs.
Comments by John P. Goldblatt, MD, and John C. Richmond, MD
The strength of this review is the comprehensive review of published studies to date, as well as the presentation of several suggestions for future studies that would serve to conclusively define the role of the MFLs. A number of theories regarding the functional role of the MFLs are summarized. One theory is that they serve a stabilizing, constraining, and possibly proprioceptive role, much like the ACL and PCL. Another idea is that they control the motion of the lateral meniscus, thereby enhancing the role of the meniscus in load distribution, while at the same time protecting the meniscus from injury. These theories are largely conjecture, and Gupte et al suggest several means to accurately prove the theories, such as a selective-cutting study. In addition, a histological examination in search of mechanoreceptors in human specimens would support the theory of proprioception.
Interestingly, one conclusion of this review suggests that precise knowledge of the function of the MFLs may result in a paradigm shift in how we treat the PCL-deficient knee. Many researchers propose that the MFLs are an integral part of the PCL complex. However, studies regarding the clinical consequence of PCL rupture fail to mention the status of the MFLs. It is possible to have complete rupture of the PCL with intact MFLs. PCL-deficient knees with intact MFLs may have a more favorable prognosis when treated nonoperatively. Clear definition of the role of the MFLs may have profound implications. PCL reconstruction may be averted if the MFLs remain intact. Or, reconstruction may be carried out in a manner to preserve the remaining fibers of the MFLs. Gupte et al conclude that a prospective clinical study examining the prognosis of PCL injuries in relation to MFL integrity would be of value.
It is suggested that the clarification of the role of the MFLs may also influence the operative approach to lateral meniscus injury. Techniques for treating posterior horn lateral meniscus tears may change, and meniscal transplantation techniques may be altered.
Dr. Goldblatt is a Fellow at Tufts University School of Medicine.
Dr. Richmond is Professor of Orthopaedic Surgery, Tufts University School of Medicine, Boston, MA.