ARTICULAR-CARTILAGE THICKNESS AND GLYCOSAMINOGLYCAN DISTRIBUTION IN THE YOUNG CANINE KNEE-JOINT AFTER REMOBILIZATION OF THE IMMOBILIZED LIMB

The recovery of articular cartilage from atrophy induced by joint immo bilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immobilization of the knee (stifle) joint of y oung dogs reduced the concentration of articular cartilage glycosamino glycans (GAGs) by 13-47%. In the present study, right hindlimbs from s ix female beagles were immobilized for 11 weeks, as in the previous st udy, and then were remobilized for 15 weeks. Cartilage from the knee j oint was compared with cartilage from nonimmobilized knees of eight ag e-matched control beagles. Histological samples taken from 11 differen t locations of the knee joint were stained with safranin O, and micros pectrophotometry was used to demonstrate distribution of GAGs in the t issue. After remobilization, GAG concentration was restored in the pat ellofemoral region and tibial condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8-26% less than the control values. On the sum mits, the thickness of the uncalcified cartilage was as much as 15% le ss than in the age-matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoratio n of articular cartilage was not obtained at all sites of the knee joi nt within the 15 weeks of remobilization. Immobilization of the skelet ally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alteratio ns are induced.