Dimorphic comparative histological and histometric study of the lateral and medial knee menisci in male and female human cadavers

The knee menisci are fibrocartilaginous discs present in between the femur and the tibia. They play a pivotal role in withstanding the weight-bearing forces and help to maintain the stability of the knee joint. Descriptive knowledge of the menisci is essential to understand the mechanism and design of the appropriate management of their pathological lesions. Several investigations have identified the anatomical and morphological differences between the medial (MMi) and lateral menisci (LMi) in humans. What remains unclear, however, is the comparative analysis of histological and histometric parameters of these menisci, especially between males and females. To evaluate and compare the different histological, histometric and biochemical parameters of different structural components (collagen, proteoglycans, cellularity, and vascularity) of MMi and LMi in male and female human cadavers, twenty-four knee joints, 12 males and 12 females, were dissected, and the menisci were excised and labeled. The middle region of each meniscus was cross-sectioned and subjected to different histological, histometric and biochemical studies. Histological examination of MMi and LMi in both males and females yielded several observations regarding different meniscal components; the orientation of collagen fibers was circumferential with intermingled radial fibers. Both fibroblasts and fibrochondrocytes were arranged singly or in rows alongside the direction of the collagen fibers. Also, the blood vessels were present toward the periphery, whereas the proteoglycans-rich areas were more evident in the inner region of each meniscus. Nevertheless, collagen fibers organization, safranin-O staining intensity, and cellular arrangement were all different between males and females. The analysis of these changes was further compared histometrically between MMI and LMi in males and females. The gained comparative histological, histometric and biochemical findings of this work are critical for providing detailed information on the microstructure and composition of both MMi and LMi in males and females. The present results also highlight the detrimental effects of histological structure on different meniscal injuries.