- The superficial (tangential) zone is the thinnest layer and provides most of the cartilage’s tensile strength and protects the deeper zones; it is primarily formed from type II and IX collagens, with fibres aligned parallel to the articular surface forming a dense mat.
- At the very surface of the gliding zone is a layer called the lamina splendens. This contains no cells, a clear film of fine collagen fibrils with little proteoglycan.
- The superficial zone has a high density of chondrocytes that synthesise high concentrations of collagen and a much lower concentration of proteoglycans.
- Good resistance to shear forces during joint movement due to tangential arrangement, greatest tensile strength.
- Low metabolic activity hence low healing potential.
- The highest concentration of collagen and the lowest concentration of proteoglycan
Figure 1. Collagen and cellular arrangement of articular cartilage
Figure 2. H&E stain and schematic representation of hyaline cartilage morphology and structure. SZ, superficial zone; MZ, middle zone; DZ, deep zone; CZ, calcified zone; SB, subchondral bone. Picture used with permission obtained from J Cytochem Biochem.