True about the anatomy of great saphenous vein-
Great saphenous vein forms as continuation of medial marginal vein to which dorsal venous arch unites. It runs in front of medial malleolus and opens into femoral vein through the saphenous opening located at 4cms below and lateral to pubic tubercle. There are about 15-20 valves in the great saphenous vein.
Starts as a continuation of medial marginal vein
Ends of femoral vein 2.5 cm below the inguinal ligament
There are 2-5 valves below the knee
Ascends 2.5-3 cm behind tibial malleolus