Ultrastructural changes in the transitional zone between articular cartilage and synovial membrane during the development of experimental osteoarthrosis.

We studied the ultrastructural changes that take place in the transitional zone between the articular cartilage and the synovial membrane during the development of experimental osteoarthrosis. We focused special attention on changes involving the proteoglycan complexes within the matrix of articular cartilage. We observed that changes in the transitional zone resemble those seen in articular cartilage during the development of osteoarthrosis. We also found transient cellular forms with fibroblast phenotype regulating the demands of both cartilage and synovial matrix. The transient nature of these elements determines the pronounced lability of this zone, and this may be related to the early development of osteoarthrosis.