A study of the structural response of wet hyaline cartilage to various loading situations.

A direct view has been obtained of the manner in which the fibrous components components and chondrocytes in hyaline cartilage respond to the application of uniaxial tensile loading and plane-strain compressive loading. A micro-mechanical testing device has been developed which inserts directly into the stage of a high-resolution optical microscope fitted with Nomarski interference contrast and this has permitted simultaneous morphological and mechanical observations to be conducted on articular cartilage maintained in its wet functional condition. Aligned and crimped fibrous arrays surround the deeper chondrocytes and can be observed to undergo well-defined geometric changes with applied stress. It is thought that these arrays may act as displacement or strain sensors transmitting mechanical information from the bulk matrix to their associated cells thus inducing a specific metabolic response. The process of tissue recovery following sustained high levels of compressive loading can also be observed with this experimental technique.