Healing of Cartilage : Wheeless' Textbook of Orthopaedics

(see also: Chondral Injuries: Nourishment)

Discussion

articular cartilage is avascular & is prevented from mounting a vascular response when there is isolated cartilage injury;
- absence of vessels w/ in cartilage imposes limitations on healing potential;
- indeed, some traumatic defects in cartilage apparently never heal;
  - chondrocytes in articular cartilage are capable of cell division & are also capable of increased proteoglycan synethesis;
  - regeneration of cartilage is slow, & highest potential for growth occurs in the perichondrium which lies at the periphery of articular cartilage;

when articular cartilage is injured, the type of healing that will take place is influenced by the depth of the injury;
extrinsic healing:
- dependent on a synovial reaction or subchondral bone being penetrated at the time of injury;
- w/ subchondral injury, capillary injury forms a fibrin clot, which is then replaced by granulation tissue and fibrocartilage;
- if defect is limited to cartilage, no blood vessels are disrupted, and inflammatory response is less intense than if injury extends through cartilage into subchondral bone, as occurs in intraarticular frx;
intrinsic healing (isolated injury):
- dependent on chondrocytes to synthesize a new matrix;
- since cartilage is largely avascular, healing is dependent on diffusion of nutrients from synovial fluid;
- potential for intrinsic healing appears somewhat limited;
- isolated injuries to cartilage (which do not extend to subchondral bone heal slowly and incompletely;

continuous passive motion can promote healing of articular cartilage;
in joints treated w/ continuous passive motion, healed articular defects where as joints that were immobilized showed no healing