Deep Vein Thrombosis
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.
Deep vein thrombosis is a serious condition because a blood clot that has formed in your vein can break loose and travel to your lungs. However, many deep vein thromboses disappear on their own.