Pathophysiology of Cartilage Injuries

Abstract

Articular cartilage lesions represent one of the major unsolved problems in orthopedic surgery due to the limited capacity of articular cartilage for self-repair following trauma. The biological response of cartilage to injury varies depending on the extent of the traumatic event. When a lesion is confined to the superficial layer, the repair process is not initiated, as the inflammatory stimulus is too weak to stimulate the resident chondrocytes surrounding the lesion; consequently, the defect persists. However, when a full-thickness lesion occurs, reaching the vessels of the subchondral bone, the inflammatory stimulus is more important. Bleeding from the bone marrow occurs, allowing the access of growth factors and reparative cells to the lesion site. These cells are mainly fibroblasts in addition to a low percentage of mesenchymal stem cells. As a result, the newly formed reparative tissue differs from the normal hyaline cartilage in term of morphology, biochemical composition, and biomechanical properties. For these reasons it is called fibrocartilage. The aim of this chapter is to review the morphology, composition, and biomechanical function of normal cartilage and to present an analysis of the response of the cartilage tissue to the different traumas.