Ultrastructural changes in synovium and cartilage in experimental hemarthrosis in dogs.

This paper reports electron-microscopic findings in synovium and cartilage in experimental hemarthrosis in dogs. The results are correlated with the total amount of glycosaminoglycans in the cartilage matrix, measured by the fixed-charge density method. Very early, changes are seen in the synoviocytes, similar to synovitis, and especially phagocytosis of iron-containing particles forming secondary lysosomes or siderosomes. Siderosomes are also a constant feature seen in the chondrocytes, together with changes in the rough endoplasmic reticulum and in the glycogen content, correlating with the changes in the ground substance.