Date Published: June 28, 2012
Publisher: Hindawi Publishing Corporation
Author(s): K. Natsis, G. Paraskevas, N. Anastasopoulos, T. Papamitsou, A. Sioga.
Purpose. A relatively unknown ligamentous structure of the posterolateral corner of the knee joint, the so-called meniscofibular ligament (MFL), was investigated as regards its macroscopic morphology, its histological features, and its reaction to knee movements. Material and Methods. MFL was exposed on 21 fresh-frozen unpaired knee joints. Its microscopic morphology was examined utilizing for comparison the fibular collateral and the popliteofibular ligament. Results. MFL was encountered in 100% of the specimens as a thin striplike fibrous band extending between the lower border of the lateral meniscus and the head of the fibula. MFL was tense during knee extension and external rotation of the tibia, whereas its histological features were similar to those of fibular collateral and popliteofibular ligament. Discussion. Its precise histological nature is studied as well as its tension alterations during knee movements. The potential functional significance of the MFL with respect to its role in avoidance of lateral meniscus and lateral coronary ligament tears is discussed. Conclusions. MFL presumably provides an additional protection to the lateral meniscus during the last stages of knee extension, as well as to the lateral coronary ligament reducing the possibility of a potential rupture.
The posterolateral corner of the knee joint is an anatomical area where serious interest has been appeared recently by anatomists as well as orthopaedic surgeons. The complexity of the anatomical structures constituting this area and the confused nomenclature of the ligaments and capsular thickenings concentrate the interest of many researchers [1–4]. Such a raised interest is due to the fact that posterolateral corner injuries with or without cruciate ligaments ruptures can lead to an unexplained instability . The posterolateral corner elements prevent varus angulation, posterior shift, and excessive external rotation of the knee .
The potential presence of the MFL at the area of the posterolateral corner of the knee joint was detected on 21 fresh-frozen unpaired knee joints utilized for educational and research purposes at the Laboratory of Anatomy of the Medical School of the Aristotle University of Thessaloniki. In specific and according to the procedure of classical method of anatomical practice, the popliteal fossa was opened by routine dissection. The superficial to the popliteus tendon anatomical structures were removed to provide a clear vision for observing the capsular and ligamentous connections of the lateral meniscus. The aforementioned connections were repeatedly recorded as photographs during the course of the dissection. Furthermore, we noticed the changes of MFL tension during knee flexion and extension. At last, we excised the MFL along with its attachments to the head of fibula and the lateral meniscus, and we conducted appropriate histological examination in order to determine the precise histological nature of MFL. For comparison we performed histological examination in sections taken by the adjacent fibular collateral and the popliteofibular ligament in order to determine more accurately the histological nature of the encountered meniscofibular band. The tissues were stained with hematoxylin and eosin. For better histological analysis of the MFL elastin staining was utilized.
In 21 examined cadaveric unpaired knee joints (11 right-sided and 10 left-sided), thus an incidence of 100%, we noticed the existence of a thin fibrous band originating from the inferior border of the lateral meniscus at the area of the posterior part of its midportion. That band, the so-called MFL, directed backwards, outwards, and inferiorly anchored ultimately to the head of the ipsilateral fibula with the knee fibrous capsule attaching just proximal to the fibular head (Figure 1). MFL was seen to reinforce the thin lateral coronary ligament, which was extended from the lateral meniscus to the lateral aspect of the lateral tibial condyle just distal to the articular margin and proximal to the knee fibrous capsule attachment (Figure 2). In only one case (4.8%) MFL was hypoplastic, being, however, distinct. Performing knee movements we observed that MFL was tense during knee extension and external rotation of the tibia, whereas it was slack during the reverse movements.
The lateral meniscus, as it is well known, is less firmly anchored than the medial one as it is attached mainly to the fibrous capsule, via weak fibers . However, lateral meniscus attachments to its neighboring structures do exist. In specific, the posterior horn is attached to the medial condyle of the femur anterior and posterior to the attachment to the posterior cruciate ligament, forming the anterior and posterior meniscofemoral ligaments [14–16]. At least one meniscofemoral ligament has been found in approximately 93% of knees, whereas 50% of them had both ligaments . These ligaments can assist to withstand tibial posterior draw  and may act as a splint to keep the posterior cruciate ligament in position while it heals after rupture . The anterior meniscofemoral ligament (of Humphrey) is slack in the extended knee and tightens with knee flexion to withstand tibial posterior draw. The converse occurs with the posterior meniscofemoral ligament of Wrisberg .
Analysing our observations one can speculate that MFL could offer protection to the lateral meniscus from likely damage during the last stages of knee extension. Moreover, MFL reinforced the posterolateral part of the lateral coronary ligament, a fact that could explain the relative low incidence of lateral coronary ligament rupture. Certainly, further investigation should be done to highlight the exact biomechanical characteristics of the MFL, as well as the likely relation or not to lateral meniscus tears, protection of the coronary ligament, and function and traumatology of the proximal tibiofibular joint.