An Ultrastructural Study of Normal Young Adult

Articular cartilage is a highly specialized connective tissue consisting of relatively small numbers of cells distributed throughout an abundant extracellular substance. The extracellular substance consists of fibrous elements, only some of which show the characteristic morphology of mature collagen, embedded in a gel-like matrix or ground substance. While our understanding of the composition and structure of the ground substance has been increased substantially in the last decade, precise descrip-tions of the different fibrous elements in human articular cartilage and of the 1)at-terns formed by these fibers in different regions are lackilig. Indeed, there has been little agreement on the part of different investigators, even in regard to the most general features of fiber architecture of human articular cartilage. Benninghoff , for example, suggested that the collagen fibers formed arcades, which were anchored deeply in the layer of calcified cartilage (Zone IV), ran ver-tically towards the surface in the radial zone (III), turned obliquely in the transi-tional zone (II), and follow-ed a horizontal course parallel to the free surface in the superficial tangential zone (I)