In severe chronic venous insufficiency (CVI) the fascia cruris is increasingly involved in the pathological process. The resulting loss of compliance as a consequence of altered fascia texture leads to increased pressure in the compartments of the lower extremity, followed by reduced circulation. Arteries and nerves, which penetrate the fascia along with insufficient perforating veins, are damaged through the increased pressure and are therefore functionally impaired. Accordingly many pathological changes in the crural ulcer have their anatomical substrate here. The microcirculation is distributed by either primary varicosis with secondary insufficiency of the deep veins or by primary insufficiency of the deep venous system as seen in a post-thrombotic syndrome. Subsequent therapy should be based on this knowledge and therefore consists of medication and basic physical therapy along with dissection of the perforating veins-fasciotomy and fasciectomy combined with plastic surgery. All of the therapeutic measures have to take the stage of the CVI into consideration. In order to eliminate the insufficient perforating veins and to perform fasciotomy the endoscopic approach is considered the state of the art. In extreme cases, only fasciectomy combined with plastic surgery can lead to durable healing.