Degenerative conditions of I the articular cartilage J

Abstract

The articular cartilage is not a simple inert bearing surface but rather a complex living tissue .It has the capacity to provide a low friction surface and distribute loads to the subchondral bone, all with a limited capacity for repair and without evidence of wear over a lifetime of use. The functional components of the articular cartilage consist of an extracellular matrix composed of a highly organized macromolecules framework filled with water and chondrocytes. The chondrocytes form the macromolecular framework of the matrix from three classes of molecules: the collagens, the proteoglycans, and the non-collagenous proteins.

Throughout life, the articular cartilage undergoes continual internal remodeling as the cells replace matrix macromolecules lost through degradation. Loading of the articular cartilage caused by joint use creates mechanical, electrical, and physicochemical signals that direct chondrocytes synthetic and degradative activity. The capacity of normal articular cartilage to provide the wear-resistant nearly frictionless bearing surface depends on the material properties of the tissue. Changes in the extracellular matrix, such as increased hydration, disruption of the collagen fibrillar network, and disaggregation and loss of proteoglycans have profound effects on the material properties of the tissue with subsequent alteration of the biomechanical properties and finally failure of the proper function as the bearing surface of the joint.