Very rapid clearance after a joint bleed in the canine knee cannot prevent adverse effects on cartilage and synovial tissue

Objective: Joint bleeding leads 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 significantly less outspoken. As a possible explanation for this discrepancy, we studied the clearance rate of blood from the canine knee joints. Methods: Blood was injected into the knee joint of Beagle dogs either 48 h, 24 h or 15 min before termination. The amount of red blood cells (RBC) and white blood cells (WBCs) 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: The amount of blood was decreased to <5% within 48 In. Within this time period the cartilage was negatively affected and the synovial tissue showed cartilage destructive activity. Evaluation of the synovial tissue 15 min post-injection revealed countless numbers of intact RBC that were almost completely disappeared after 48 h without significant recruitment of macrophages. Conclusions: Blood is cleared very rapidly from the canine knee joint, but already has adverse effects on both cartilage and synovial tissue within that short time span. 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 present for at least 48 h is needed to induce long-term adverse effects in vitro. (C) 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.