Abstract
The ultrastructure of the amorphous layer (AL) of the articular cartilage surface was investigated by quick-freezing and deep-etching and immunohistochemistry. The uppermost layer of cartilage, which is generally assumed to be amorphous, forms a three-dimensional network of fine filaments, 10-15 nm in diameter. Immunohistochemistry demonstrated that type VI collagen was involved in the AL formation, of sugesting that the AL may correspond to the uppermost layer of the synovial membrane. This also suggested that some components of the synovial membrane remained as remnants on the surface of articular cartilages. Moreover, the density of immunogold staining for fibronectin was much lower in the normal AL than in the cartilagenous superficial layer, but the fbronectin in the AL was densely immunolocalized at some sites of cartilagenous degeneration.
