Figure 4.

(A) Magnetic resonance image of a rat knee with medial meniscal tear: a cyst is seen in the epiphysis of the tibia (white arrow). (B) Haematoxylin and eosin histology (low power magnification at original magnification × 25, and medium power magnification insert at original magnification × 100) of the medial femorotibial following meniscal transection. The articular cartilage of the tibia shows loss of chondrocytes (arrowhead) and staining pallor reflecting loss of proteoglycan (arrow). There is a vertical fracture in the degenerate cartilage and underlying focal loss of subchondral bone with extrusion of the degenerate matrix through into the marrow space. There is an associated loss of the normal marrow cellularity in the insert region with replacement by cellular infiltrates and fibrous tissue, resulting in epiphyseal cyst formation (insert). MFC = medial femur condyle.