Papain-induced changes in the knee joints of adult rabbits.

Rapidly progressing joint disease can be produced in the rabbit by intra-articular injection of concentrated papain. With the use of radioactive thymidine it is possible to demonstrate that the cartilage cells recover their ability to divide by mitosis at the same time as degenerative changes appear in the cartilage. Clusters of chondrocytes arise by mitosis of chondrocytes and not by a floating together of cartilage cells.