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Healing of Cartilage

(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;

mechanisms of repair

  • 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:

  • 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

References