Early changes in the ground substance of articular cartilage in experimental hemarthrosis in dogs, measured by the fixed-charge density method.

This work presents early findings in the articular cartilage of dog knees in experimental hemarthrosis produced by injections of whole blood, red blood cells, white blood cells, serum, and iron citrate. The effect of coagulation and synovectomy was also studied. The fixed-charge density determination has proved to be a reliable, easy, and rapid method for finding - very early in the process - quantitative changes in cartilage ground substance. Changes in the proteoglycan (PG) content of articular cartilage matrix take place after a certain duration and intensity of hemarthrosis, after which loss of ground substance is repeatedly and consistently observed. After some time (6 months, and culminating after 14 months in our study) a reparative reaction takes place. In experimental hemarthrosis of longer duration this healing reaction seems to be overwhelmed by the degrading forces, with probable further evolution to the full-blown pathology. The cellular components of the blood seem to play a major role. Prophylactic synovectomy seems to be effective only in preventing further bleeding. Coagulation of the intra-articular blood does not alter its deleterious effect. Finally, a small iron ligand alone, although proven in vitro to penetrate into cartilage, is not capable of producing matrix changes.