Postural obstruction of the popliteal vein. Its role in deep venous insufficiency of the legs]

Postural or, more generally, positional obstruction of the popliteal vein occurs either in complete extension of the leg, or in powerful flexion of the order of 90 degrees. It is sometimes constitutional and sometimes acquired, as a result of dystrophy of the venous wall. Abnormal phlebographic appearances vary according to the position of the leg and the level of the obstruction: signs of narrowing or axis displacement with the knee in extension; plications, sinuousities, stenosis, curved imprints with the knee in flexion. The actual existence of circulatory slowing has been confirmed by Doppler. Hemodynamic consequences appear to be all the more severe when the obstruction is tighter, situated higher and when the great saphenous itself is narrowed at the level of the popliteal crease. Despite its intermittent nature, positional obstruction must be kept under consideration: in hospital medicine, because of the potential danger of venous stasis which it causes, with the risk of underlying thrombosis; in everyday phlebology, since it explains, to a certain extent, the mechanisms of chronic venous insufficiency occurring after standing upright or sitting for prolonged periods. Awareness of this possibility forms the basis of a number of general rules concerning good venous health, certainly by no means original but rarely observed.