Fig. 1

Full-thickness section cut perpendicular to the surface of a discoid lateral meniscus in a 13-year old patient (5× magnification, H&E). Within the fibrocartilaginous tissue, was possible to see a different architecture between the femoral and the tibial surface. In fact, while the tibial surface was smooth and free of irregularities, the femoral surface appeared wavy, with some clefts. Furthermore the orientation of the collagen fibers varied from the periphery to the center of the tissue. While on the periphery the collagen fibers were oriented parallel to the surface, in the inner part of the tissue a random orientation was observed with an interwoven tighter network of collagen fibers. Moreover, in some areas of the tissue, degeneration could be seen, with an extracellular matrix showing a lower intensity of staining with totally disorganized collagen fibers. The upper left box showed the same case at a greater magnification. On the articular side, cells had a more flattened morphology, with the major axis parallel to the surface (arrow). In contrast, cells in the central portion appeared more round. It was possible to see several tears due to tissue damage (asterisk). Cells were scattered inside the different portions of the tissue with some areas of hypo-cellularity or totally devoid of cells as a sign of degeneration