Among the joint and muscle pumps that are hemodynamically active and, in particular, bring about venous return in the lower limb, the so-called ankle pump is of paramount importance. The basic anatomical relationship of the talocrural joint to the venous network around the ankle is reviewed. Duplex sonographic measurement of the rate of blood flow in the great saphenous vein at the saphenous opening, at rest and during active and passive movements at the ankle joint, shows that such movements have an important effect on the rate of flow through the adjacent veins. Passive movement of the foot relative to the leg was brought about by a newly developed apparatus that can be either pneumatically or electrically operated. The action of the ankle pump against venous stasis, the arthrogenic congestive syndrome, and chronic venous insufficiency has demonstrated the prophylactic importance of this physiological mechanism. It can, when necessary, be replaced by an appropriately designed apparatus.