At the ankle, the great saphenous vein receives branches from the sole of the foot through the medial marginal vein; in the lower leg it anastomoses freely with the small saphenous vein, communicates by perforator veins (Cockett perforators) with the anterior and posterior tibial veins and receives many cutaneous veins; near the knee it communicates with the popliteal vein by the Boyd perforator, in the thigh it communicates with the femoral vein by perforator veins (Dodd perforator) and receives numerous tributaries; those from the medial and posterior parts of the thigh frequently unite to form a large accessory saphenous vein which joins the main vein near the sapheno-femoral junction.