Pathophysiology of cartilage injuries

[Machine translation] The articular cartilage lesions represent one of the major unsolved problems in the orthopaedic surgery. This is because articular cartilage has a limited capacity of self-repair following trauma. The biological response of cartilage to injury varies in the different traumatic events. When a lesion is confined in the superficial layer, the repair process does not occur, as the inflammatory stimulus is too weak to stimulate the resident chondrocytes surrounding the lesion and, consequently, the defect persists. However, when a full-thickness lesion occurs reaching the vessels of the sub-chondral bone, the inflammatory stimulus is more important, a bleeding from the bone marrow occurs allowing the access of growth factors and reparative cells in the lesion site. These cells are mainly fibroblasts and in a low percentage 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. Moreover, an analysis of the response of the cartilage tissue to the different traumas is presented.
The articular cartilage lesions represent one of the major unsolved problems in the orthopaedic surgery. This is because articular cartilage has a limited capacity of self-repair following trauma. The biological response of cartilage to injury varies in the different traumatic events. When a lesion is confined in the superficial layer, the repair process does not occur, as the inflammatory stimulus is too weak to stimulate the resident chondrocytes surrounding the lesion and, consequently, the defect persists. However, when a full-thickness lesion occurs reaching the vessels of the sub-chondral bone, the inflammatory stimulus is more important, a bleeding from the bone marrow occurs allowing the access of growth factors and reparative cells in the lesion site. These cells are mainly fibroblasts and in a low percentage 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. Moreover, an analysis of the response of the cartilage tissue to the different traumas is presented.