What are the practical differences between arterial and venous thrombosis?

Very different : Venous thrombosis is often painful and can cause swelling in the legs, but is rarely life or limb threatening unless associated with pulmonary embolism. Arterial thrombosis however is almost always a vascular emergency. Without adequate artery circulation, the end organ ( leg, arm, kidney, brain, heart) begins to suffer and tissue begins to die. If treated quickly, recovery is possible.

Different outcome: Arterial thrombosis occurs when there is stoppage of blood flow in an artery due to arteriosclerosis or embolus. The part that is fed by the artery is injured by the lack of blood supply. Venous thrombosis comes on after there is stagnant flow, injury to the vein lining, and abnormalities in blood components. There is local pain, but rarely tissue injury.