A complete understanding of precisely how compression works remains unknown. Two actions are generally accepted. Probably the most beneficial effects of compression are its effects on the capillaries and tissue spaces.

Compression is believed to increase the pressure in the tissues beneath the skin thus reducing excess leakage of fluid from the capillaries and increasing absorption of tissue fluid by the capillaries and lymphatic vessels. Compression therefore reduces and helps prevent swelling.

The physical presence of the stocking also helps control the size (diameter) of superficial veins beneath the stocking. The stocking does not allow these superficial veins to over expand with blood. This action helps prevent "pooling". The venous blood then flows more quickly up the leg towards the heart.