[The action of deep venous insufficiency at the popliteal level on the junction of the external saphenous vein and the gemellary veins].

Duplex-ultrasound and colour-ultrasound have enabled successful close study of valve patency and function by the analysis of hemodynamic changes: direction, velocity, circulatory conditions. Direction by colours: red attributed to arriving flow and blue to outflow. Circulatory velocity by the intensity and brilliance of colours. Circulatory conditions by the colour green revealing the existence of a turbulent flow, with anterograde turbulent flow coloured yellow and retrograde turbulent flow turquoise. A so-called mosaic pattern occurs when turbulent flow has a high circulatory velocity. Investigation of the popliteal vein: patient in ventral horizontal and standing positions. Normal morphological characteristics: Course essentially straight. Valve system proximal to the junction of the small saphenous. Anteroposterior diameter: less than 1 cm in horizontal position, less than 1.5 cm standing. Totally compressible by external pressure and partially by hyperextension of the ring of soleus. Characteristics of popliteal insufficiency: increased calibre--positive compressibility--duplication of standing calibre--pulsed Doppler with a biphasic wave--colour--ultrasound with reflux red--turbulent conditions and mosaic pattern may be present. Investigation of the small saphenous vein: enables determination of morphological characteristics, the site of the junction, detection of reflux and measurement of its degree. Valve insufficiency of the popliteal vein may form part of a syndrome of overall insufficiency of the deep system, primary or secondary, depending upon one valve only, located proximal to the junction of the small saphenous. When this functions badly, special reflux circuits develop, with the outcome depending on the course which these circuits may take.