Remodelling in immature hyaline cartilage: changes in matrix dry mass

Scanning microinterferometric measurements were made of matrix dry mass in the intermediate layer of normal rabbit patellar articular cartilage and in the area surrounding standard, experimental, full-thickness lesions of 1-5 mm diameter. The lesions were created in 1 kg animals and were allowed to heal for up to 3 weeks. Changes in matrix dry mass were recorded in predetermined zones around the lesions immediately after surgery, and at 1 week, and at 3 weeks post-operatively. After 1 week the rapid early fall in matrix solids was partly offset in areas corresponding to a zone of locally proliferating chondrocytes which appeared to maintain the matrix dry mass close to normal levels. The maximal fall occurred at the extreme edge of the lesion where, it is suggested, total glycosaminoglycan loss had taken place. After 3 weeks the matrix dry mass values had risen to the normal range, apart from a narrow zone adjacent to the wound edge. The findings are discussed in the light of previous quantitative work on the composition of articular cartilage and on the nature of the reactions of cartilage to injury.