Three-dimensional imaging analysis of the developmental process of posterior meniscofemoral ligaments in rat embryos.

Introduction: The posterior meniscofemoral ligament (pMFL) of knee joint is a ligament that runs posterior to the posterior cruciate ligament (PCL) and it is known that the height of the pMFL attachment site causes meniscus avulsion. Therefore, understanding the three-dimensional (3D) structure of the pMFL attachment site is essential to better understand the pathogenesis of meniscus disorders. However, the developmental process of pMFL has not been well investigated. The purpose of this study was to analyze pMFL development in rat knee joints using 3D reconstructed images produced from episcopic fluorescence image capture (EFIC) images and examine its relationship with other knee joint components.

Methods: Knee joints of Wistar rat embryos between embryonic day (E) 16 and E21 were observed with HE stained tissues. Serial EFIC images of the hindlimbs of E17-E21 were respectively captured, from which 3D images were reconstructed and the features of pMFL structure: length and angle, were measured. Besides, the chronological volume changes and the volume ratio of the knee joint components compared to E17 were calculated to identify the differences in growth by components.

Results: pMFL was observed from E17 and was attached to the medial femoral condyle and lateral meniscus at all developmental stages, as in mature rats. The lack of marked variation in the attachment site and angle of the pMFL with the developmental stage indicates that the pMFL and surrounding knee joint components developed while maintaining their positional relationship from the onset of development.

Conclusion: Current results may support to congenital etiology of meniscus disorder.