This study defined certain aspects of the effect of repeated hemarthroses on the articular cartilage and synovial tissues of the knee joints of New Zealand white rabbits. Twenty-eight animals received injections twice a day of unclotted homologous blood for up to eight weeks. The animals were killed serially beginning at one day and the synovial membrane and cartilage were resected for histological, histochemical, and biochemical study.

The synovial tissues demonstrated the classic changes of inflammation followed by progressive fibrosis, scarring, and deposition of iron. In the cartilage, there was no significant change in the microscopic appearance of the cells or matrix nor was there deposition of iron. The metabolic activity of the cartilage was quantitatively assayed by determinations of the rates of synthesis of ribonucleic acid and protein (as measured by in vitro incorporation of glycine-H³ and cytidine-H³, respectively), and there was essentially no change noted during the eight weeks of the study.

It was concluded that repeated hemarthroses over an eight-week period have a profound effect on synovial tissues but little or no effect on the histological, histochemical, or metabolic activity of cartilage. From these data it is speculated that cartilage damage, so common in hemophilia, probably requires more than just the presence of blood, and that hemarthrosis (or hemarthroses) may not be particularly harmful to the articular surfaces of a joint.