The limb is elevated and an elastic bandage is applied firmly from the toes to the upper 1/3 of the thigh to obliterate the superficial veins only.
If deep system is competent, the blood will go through and back to the heart.
If the deep system is Blocked(has a thrombus), the patient will feel pain in the leg.
The test is done by applying a tourniquet at the level of the sapheno-femoral junction to occlude the superficial pathway, and then the patient is asked to move in situ.
The Trendelenberg procedure so as to ascertain the patency of deep venous system before removing or ligating the superficial system This is a more objective test as it does not depend on patient's pain threshold.