Neural Structures within Human Meniscofemoral Ligaments: A Cadaveric Study

Aim. To investigate the existence of neural structures within the meniscofemoral ligaments (MFLs) of the human knee. Methods. The MFLs from 8 human cadaveric knees were harvested. 5？μm sections were H&E-stained and examined under light microscopy. The harvested ligaments were then stained using an S100 monoclonal antibody utilising the ABC technique to detect neural components. Further examination was performed on 60–80？nm sections under electron microscopy. Results. Of the 8 knees, 6 were suitable for examination. From these both MFLs existed in 3, only anterior MFLs were present in 2, and an isolated posterior MFL existed in 1. Out of the 9？MFLs, 4 demonstrated neural structures on light and electron microscopy and this was confirmed with S100 staining. The ultrastructure of these neural components was morphologically similar to mechanoreceptors. Conclusion. Neural structures are present in MFLs near to their meniscal attachments. It is likely that the meniscofemoral ligaments contribute not only as passive secondary restraints to posterior draw but more importantly to proprioception and may therefore play an active role in providing a neurosensory feedback loop. This may be particularly important when the primary restraint has reduced function as in the posterior cruciate ligament—deficient human knee. 1. Introduction The knee joint is stabilised by passive restraints, such as the capsule and ligaments, as well as active restraints. It has been suggested that the ligaments of the knee may contribute to active stability by providing proprioceptive input to the nervous system, which in turn would adjust muscle contraction accordingly [1]. The anatomy of the meniscofemoral ligament (MFL) has previously been described [2]; the femoral origins of the anterior MFL are distal to the PCL, close to the articular cartilage, whereas the posterior MFL arises proximal to the PCL. They are both inserted distally to the posterior horn of the lateral meniscus. It has been shown that the mechanical role of the meniscofemoral ligament (MFL) is to resist anteroposterior and rotatory laxity in the knee. This is the most important when the primary stabiliser of posterior laxity, the posterior cruciate ligament, is deficient [3]. Proprioceptive nerve endings were initially thought to be located in muscles (as muscle spindles) [4]. More recently, mechanoreceptors have been found in the cruciate ligaments of both animals and humans [1, 5–7]. Kennedy et al. found mechanoreceptors within multiple clefts at the tibial attachment of the anterior cruciate ligament (ACL), within