Explanation of the pathomechanism of varicous morphologies. (a) Reticular vein plaque at surfacing of an incompetent perforant vein. (b) Reticular vein plaque fed by a more or less superficial “feeder vein”. (c) Spider veins at surfacing of an incompetent perforant vein. (d) Undulating course as a result of morphological enlargement of certain branches in a reticular vein network. (e) Undulating course of a larger saphenous vein branch as a result of morphological lateral “drag” exerted by a side branch with substantially elevated flow. (f) Suggested mechanism how inhomogenous contraction of antigravitational muscles can induce flow obstacle accompanied with high transmural pressures in perforant veins. Strong isometric contraction (deep brown) practically closes upward flow in deep vein main branch. Periodic or lighter contractions in muscle mass below (light brown) then pump blood in the reverse direction, toward the superficial network and produce incompetent perforantes.