Tritiated thymidine was injected into the knee joints of four older but still immature rabbits and four mature rabbits. Autoradiographs were made and exposures over cell nuclei were interpreted as indicating cell division and growth.
In the older but still immature animals, evidence of growth was confined to the basal layers of the cartilage adjacent to the layer of calcified cartilage. No exposures were noted in the articular cartilage of the adult animal.
On the basis of these data and several histological observations, certain generalizations were made regarding the changes occurring in articular cartilage of rabbits with aging. In addition, amitosis was discussed and it was concluded, on the basis of these studies, that amitosis does not represent a means of cartilage proliferation.