I read that blood clots are very common after knee joint replacements. How often does this happen and what causes it?

Actually, doctors report the chances of a blood clot after a total knee replacement (TKR) are very high. The medical term for this is deep venous thrombosis (DVT). One study reported DVT occurs in at least 50 per cent of all patients.

There’s a lot of trauma that occurs to the blood vessels of the leg during this operation. The doctor must cut through soft tissue and blood vessels to get down to the bone and joint. A tourniquet is used above the knee and this adds to the problem.

Taking the old joint out and putting a new joint in requires a lot of force. The leg is twisted and turned, pushed and pounded. Since the risk of DVT is so high, prevention is started before the operation even begins.