Q. Why are blood clots dangerous after lower extremity joint replacement surgery?

A. Blood clots can occur in either arteries or veins of the lower extremities after hip or knee replacement. While arterial blood clots are the most dangerous to the survival of the extremity itself, it is clots in the veins that have the greatest statistical potential for death.

The danger related to venous blood clots is that they can break free from their location in the leg and go into the lung where they can shut down heart and lung function. Clots that form in the arbiters of the lower extremities can damage circulation to the extremity but they are unable to migrate out of the leg. It is movement of a clot from the veins of the leg into the lung that can potentially be fatal. Statistically the likelihood of dying as the result of a blood clot to the lung is very low (much less that 1%). Nonetheless, the potential for this catastrophic event is the basis for the use of various types of blood thinners as well as other modalities in the postoperative period following hip and knee replacement. Increased awareness coupled with preventative treatment have combined to minimize the risks associated with lower extremity joint replacement, allowing these procedures to be done in steadily increasing numbers with great success.

Victor J. Faralli, M.D.