Figure 6

A schematic structure of the collagen network in AC shows that the interwoven collagen bundles in the lamina splendens integrate the obliquely oriented collagen fibres and those in the deeper region to form a 3D collagen scaffold, which anchors to the subchondral bone. It is well accepted that the 3D collagen scaffold arched on the subchondral bone of AC. It reinforces the swelling pressure of proteoglycan (PG) gel to provide the AC with loading capacities and considerable tensile strength to withstand for wear and shear stresses. Peeling off the lamina splendens where the interwoven collagen bundles reside reduces the wear and shearing resistance of the AC. It also leads to change of the osmotic pressure in AC and gradually release of PGs to the joint cavity. The tensile strength and lateral integrity of the interwoven collagen bundles permitted peeling off the most superficial layer from AC. This explains why torn articular surface occurs during excessive sports and exercises.