The Young Orthopod

Function of synovial joints, for example, the hip or the knee, depends on the unique mechanical properties of the articular cartilage that forms their bearing surfaces.  It distributes loads , thereby minimizing stresses on subchondral bone.   When loaded, it deforms and when unloaded, it regains it original shape .  It provides a surface with almost unequalled gliding properties and has remarkable durability . Although only a few millimeters thick , articular cartilage has an elaborate internal organization.  This organization can be described by dividing articular cartilage into four successive zones beginning at the joint surface :  The Superficial Or Gliding Zone The Intermediate, Middle Or Transitional Zone The Deep Or Radial Zone The Calcified Cartilage Zone  Within zones, differences in matrix composition and organization distinguish 3 regions: The Pericellular Region  The Territorial Region The Interterritorial Region. Cartilage Zones Cartilage

Gross Anatomy Five regions characterize long bones: the bulbous, articular cartilage-covered ends ( epiphyses ) tapering to the funnel-shaped metaphyses , with the central diaphysis interposed between the metaphyses.  During growth , the epiphyseal and metaphyseal regions are separated by the organized cartilaginous physis , which is the major contributor to longitudinal growth of the bone . Epiphysis incorporates the growth plate or physis and the secondary ossification center The larger long bones (clavicle, humerus, radius, ulna, femur, tibia, and fibula) have physes at both ends , whereas the smaller tubular bones (metacarpals, metatarsals, and phalanges) usually have a physis at one end only . At birth, with the exception of the distal femur and occasionally the proximal tibia, all of the above-mentioned epiphyses are purely cartilaginous .  At various stages of postnatal growth and development, a secondary ossification center forms within the epiphysis.  This dev