DECREASED BIREFRINGENCE OF THE SUPERFICIAL ZONE COLLAGEN NETWORK IN THE CANINE KNEE (STIFLE) ARTICULAR-CARTILAGE AFTER LONG-DISTANCE RUNNING TRAINING, DETECTED BY QUANTITATIVE POLARIZED-LIGHT MICROSCOPY

Objective-To investigate the effects of a one year programme of runnin g training (up to 40 km/day for 15 weeks) on the spatial orientation p attern of collagen and glycosaminoglycans in articular cartilage in di fferent parts of the knee (stifle) and shoulder joints of young beagle dogs. Methods-Area specific measurements of the optical path differen ce (= retardation, Gamma) and the cartilage zone thickness were perfor med using conventional procedures and a new computer based quantitativ e polarised light microscopy method. Transmission electron microscopy was used to determine the zonal volume density of collagen fibrils. Th e concentrations of collagen and hydroxypyridinium crosslinks were inv estigated biochemically. Results-Running training decreased Gamma by 2 4-34% (p < 0.05) in the superficial zone of the lateral femoral condyl e articular cartilage and at the centre of the tibial condyles. Gamma of glycosaminoglycans decreased by 26% (p < 0.05) in the superficial z one of the lateral condyle of the femur, but at the same site the volu me density of collagen fibrils was unchanged. Neither the collagen con centration nor the concentration of hydroxypyridinium crosslinks was a ltered as a result of running. In both control and runner dogs, the th ickness and Gamma values of the superficial zone were greater in the h umerus and the femur than in the tibia. Conclusion-Endurance type runn ing exercise in beagles caused a reduction in the superficial zone bir efringence of the articular cartilage, which indicates either a disorg anisation or a reorientation of the Hungary superficial zone collagen network. Articular cartilage showed marked variability of collagen net work organisation over the different knee (stifle) joint articular sur faces.