Three factors predispose patients to thrombosis: stasis, hypercoagulability, and vessel wall injury. Collectively, these are known as Virchow's triad. When these factors intersect, they significantly increase the risk of thrombosis.

Stasis occurs when blood flow is sluggish or halted, often due to prolonged immobilization, such as during hospitalisation or extended bed rest. This lack of movement can cause blood to pool, particularly in the legs, leading to clot formation.

Vessel wall injury refers to any damage to the inner lining of blood vessels. This can result from physical trauma, such as a calf injury, surgery, or the insertion of intravenous catheters. When the vessel wall is injured, it triggers the body's clotting mechanisms as part of the repair process, which can inadvertently lead to thrombosis.

Hypercoagulability is a state where the blood has an increased tendency to clot. This can be due to genetic conditions, such as Factor V Leiden, or acquired conditions like cancer, pregnancy, or the use of certain medications (e.g., oral contraceptives). Disorders in blood clotting can significantly elevate the risk of developing thrombosis.

Understanding Virchow's triad is crucial for identifying patients at risk for thrombosis. By recognising and addressing these factors, healthcare providers can implement preventive measures to reduce the incidence of thrombotic events, thereby improving patient outcomes.