Purpose Joint bleeds lead to joint destruction. In vitro exposure of human and canine cartilage to blood results in long lasting severe adverse changes in cartilage. An in vivo joint haemorrhage in the canine knee joint demonstrates similar adverse effects although less outspoken and long-lasting. We investigated the clearance rate of blood from canine knee joints as a possible explanation for this discrepancy.

Methods Blood was injected into the knee joint of Beagle dogs, either 48h, 24h or 15m before termination. The amount of red and white blood cells present in the joint cavity was determined. Chondrocyte activity and cartilage matrix integrity as well as cartilage destructive activity of synovial tissue were determined biochemically. Additionally, synovial tissue was analyzed by use of histochemistry.

Results Fifteen minutes after the injection of autologous blood, the red blood cell count was 5,7*1012/L, comparable to the amount present in whole blood, and gradually decreased (1,6*1012/L at 24 hours) to 0,2*1012/L within 48 hours (less than 5%). The amount of white blood cells increased in the first 24 hours, and was still increased after 48 hours, although less than after 24 hours. The proteoglycan synthesis rate and -release were adversely affected already within 24 hours (−22% and +24% respectively), and these effects were more severe 48 hours post-injection (−34% and +53% resp.). Synovial tissue culture supernatants demonstrate cartilage destructive properties as expressed by an increased release, a decreased synthesis rate, and decreased content of cartilage proteoglycans; increasing with time after the experimental haemorrhage (+207%/+247%; −58%/−62%; −8%/−28% respectively, for 24/48 hours). Evaluation of the synovial tissue revealed at 15 minutes post-injection countless numbers of intact RBC that were almost completely disappared after 48 hours, withonly limited recruitment of macrophages and iron deposition.

Conclusions Blood is cleared very rapidly from the canine knee joint, but in that short time span already has adverse effects on both cartilage and synovial tissue. This rapid clearance can play a role in the discrepancy between long-term in vitro and in vivo effects of blood-induced joint damage since more than 10% v/v blood for 48 hours is needed induced to long-term adverse effects in vitro. Irrespectively, blood has devastating effects on articular cartilage very rapidly, and in this respect it is important to prevent (traumatic) joint haemorrhages and if they occur, to treat them properly.

Disclosures: No relevant conflicts of interest to declare.

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