The effects of freezing localized areas of rabbit articular cartilage in
vivo were studied at two to twelve months morphologically (gross and
microscopic examination, including scanning electron microscopy),
histochemically (toluidine blue and safranin O), and metabolically (35S
uptake). Up to six months the frozen cartilage was intact but appeared to
be dead, as shown by the absence of stainable chondrocytes, severely
decreased acid mucopolysaccharide content, and absence of significant
uptake of 35S. At twelve months fibrillation and softening were evident,
clusters of new chondrocytes with surrounding acid mucopolysaccharides were
visible microscopically, and scanning electron microscopy revealed an
irregular pattern of collagen fibers which were larger than normal, of
varying thickness, and broken in some areas. These changes resembled those
seen in degenerative joint disease.