Effects of immobilization on the articular cartilage in young rabbits. A quantitative light microscopic stereological study.

Eight young New Zealand White rabbits were immobilized by splinting the hind limb to extension for eight weeks. Eight mobile animals served as controls. The articular cartilage of the lateral tibial condyle of control and of both splinted and contralateral knee joints were studied using a stereological method, which allowed the authors to derive, from quantitative histologic measurements, three-dimensional parameters defining the tissue structure. Qualitatively, osteoarthrotic changes occurred in both the splinted and the contralateral knee joints. Quantitatively, osteoarthrotic changes produced an increase in cell density but a decrease in cell size in the superficial zone of articular cartilage, and an increase in cell size in the deep zone. Combined qualitative and quantitative histologic characteristics were also analyzed. Different types of osteoarthrosis were observed in the splinted and the contralateral knees.