Aseptic necrosis of the femoral head appears to have a number of etiological factors. The last steps of the pathogenetic course of events, however, is unclear. Histologically, small foci of marrow necrosis form repeatedly, particularly in the upper and medial zone of charge, and then fuse secondarily to larger areas. Secondary reparation events with ingrowth of sprouts of granulation tissue and neoformation of bone predominantly in connection with necrotic trabeculi are followed by renewed waves of necrosis, resulting in a most variegated picture in which the different phases can no longer be clearly differentiated. After the articular cartilage has been sequestrated and torn away, the uncovered spongious bone is exposed to the transforming influence of direct charge, with subsequent secondary osteoarthrosis. From the histological picture follows the modern conception of its pathogenesis: an intraosseous increase in pressure primarily infringes on the venous outflow and secondarily on the arterial inflow. These cyclic circulatory disturbances provoke the focal appearance of necrosis. As a result of this, "core decompression" follows as a therapeutic intervention that is successful in many cases.