Deep Vein Thrombosis is also known as a DVT. 

A Deep Vein Thrombosis is a life-threatening condition that occurs when a vein deep in the body is blocked by a blood clot, or thrombus.

Deep Vein Thrombosis is generally found in the leg, usually in the calf muscle, or thigh and hip area, but it can happen anywhere in the body.

These blood clots usually begin in areas where the ability of the blood to clot is out of balance, or where blood flow is stopped or decreased; for example: when there is an injury to the blood vessel wall.