| Abstract
| - Background. Joint bleeding due to trauma, major joint surgery, or haemophilia leads to joint damage. However, it is unclear if there are differences between coagulating blood and anticoagulated blood with respect to joint degeneration, especially in vivo. Objectives. In a canine in vivo model we evaluated whether intra-articular blood exposure is more destructive in case of coagulating blood compared to anticoagulated blood, and whether inflammation plays a role in the cartilage damaging process. Methods. In 7 dogs left knees were injected with coagulating blood 4 times a week in week 1 and 4; right knees with saline. In 7 other dogs anticoagulated, heparinized blood was injected with heparinized saline as control. Ten weeks after the last injection cartilage matrix turnover and synovial inflammation were analyzed ex vivo. To study cartilage damage without involvement of synovial inflammation, healthy full thickness human cartilage explants were exposed in vitro to coagulating and anticoagulated blood for 4 days (n=6). Cartilage matrix turnover was determined at day 16. Results. Canine knees injected with coagulating blood showed an increase of both newly formed and total (resident) glycosaminoglycans of 9% and 15%, respectively (p=0.04 and p=0.01, respectively), as well as a decreased proteoglycan content of 6%. Injection with coagulating and anticoagulated blood caused an increase of proteoglycan synthesis rate of 24% and 14%, respectively (p=0.01 and p=0.04, respectively), as a characteristic of (ineffective) repair activity. Intra-articular injections with coagulating blood led to more synovial inflammation on macroscopy as well as histology (p<0.001and p=0.01, respectively), in contrast to knees injected with anticoagulated blood. Coagulation of blood in vitro resulted in more cartilage damage compared to anticoagulated blood. This was expressed as more reduction of proteoglycan synthesis rate by coagulating blood compared to anticoagulated blood (17% difference; p=0.05), and a higher release of proteoglycans after exposure to coagulating blood compared to anticoagulated blood (94% difference; p=0.01). Conclusions. This study shows that coagulating blood causes more long-lasting in vivo joint damage than anticoagulated blood; directly on cartilage and via inflammation. In case of joint surgery prolonged anticoagulation might limit the harmful effects of intra-articular blood. Moreover, aspiration of blood would prevent joint damage. Disclosure of Interest. None Declared
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