Deep vein thrombosis (DVT) is a condition in which a blood clot (thrombus) forms in one or more of the deep veins in your body, usually in your legs. Deep vein thrombosis can cause leg pain, but often occurs without any symptoms.
Deep vein thrombosis can develop if you're sitting still for a long time, such as when traveling by plane or car, or if you have certain medical conditions that affect how your blood clots.
If a blood clot (thrombus) forms in the one of the body's veins (deep vein thrombosis or DVT), it has the potential to break off and enter the circulatory system and travel (or embolize) through the heart and become lodged in the one of the branches of the pulmonary artery of the lung. A clot that travels through the circulatory system to another location is known as an embolus (plural emboli).