Thrombosis is the medical term for the formation of a blood clot in a blood vessel. In deep vein thrombosis (DVT), the blood clot forms in one of the larger, deeper veins that run through the muscles. Deep vein thrombosis usually occurs in the lower leg.
It often goes unnoticed and dissolves on its own. But it may cause symptoms like pain and swelling. If someone is diagnosed with DVT, they will need treatment to avoid serious complications such as pulmonary embolism. This can occur if the blood clot breaks away from its original site and is carried to the lungs in the bloodstream.
The risk of deep vein thrombosis increases after more major operations such as knee or hip replacement surgery. Because of this, people who have had this kind of surgery are usually given medication to prevent blood clots from forming.