Methods for cartilage and subchondral bone histomorphometry

This chapter presents the histological assessment of cartilage and bone of tibial plateaus, by procedures that have been applied and validated in two animal models of osteoarthritis: meniscectomized rats and guinea pigs. It starts from bone sampling, followed by all the steps of sample preparation from embedding to sectioning (without prior decalcification), staining, and mounting. Depending on the cartilage or bone components to be visualized, two dyes are described: safranin O and Goldner's trichrome. On these stained sections, various histomorphometric parameters are then quantified using the dedicated programs of an image analyzer. The following parameters are evaluated at the medial side of the tibia and are described at the levels of both cartilage (cartilage thickness, fibrillation index, proteoglycan content ratio based on safranin-O staining intensities and chondrocyte density) and bone (subchondral bone plate thickness).