THE PERMEABILITY OF ARTICULAR CARTILAGE

Abstract

1. We have shown that the permeability of cartilage is the same in necropsy specimens as in the living animal. We have concluded that studies of material transport into cartilage carried out on necropsy specimens validly reflect in vivo conditions. 2. We have studied the effect of agitation of the fluid in which cartilage is immersed upon the rate of diffusion of substances into cartilage and have found that agitation increases the rate of penetration up to three or four fold. We believe that it may be inferred from this fact that the nutrition of cartilage is partly dependent on joint movement. 3. We have examined the permeability of the bone-cartilage interface to water and solutes and have found that in the adult no detectable material transfer occurs across this zone. In the child on the other hand the bone-cartilage interface appears to be permeable to water and solutes. 4. We have measured the diffusion coefficient of glucose in cartilage and have hence estimated the depth of cartilage which can be adequately supplied with glucose from the synovial fluid in the presence and absence of agitation. 5. We have examined both experimentally and theoretically the possible effect of intermittent loading on the rate of penetration of substances into cartilage. We have concluded that at low pressures intermittent loading contributes little to the material transfer into cartilage. At high pressures intermittent loading does lead to the transport of solutes into cartilage but it cannot significantly increase the rate of transfer above that attributable to normal diffusion. Loading cartilage surfaces for prolonged periods of time without allowing intermittent relaxation would be expected to lead to decreased diffusion, without any absorption of fresh fluid attributable to the action of a pump, and would thus result in an overall decrease in the rate of penetration of substances into cartilage.