Fifty patients (forty-four male and six female) with non-traumatic necrosis of the femoral head underwent evaluation at the University of Iowa Hospitals between 1951 and 1968. Their average age was forty-six years. There was bilateral involvement in thirty-six patients (72 per cent).

Associated diseases of statistical significance included heavy alcohol consumption in thirty-seven patients, gout in ten, and hyperuricemia in ten. These and other associated diseases are often accompanied by disturbances in clotting mechanisms. The association constitutes indirect evidence for the existensce of a bleeding or clotting defect in forty-eight of the fifty patients.

Direct evidence for a clotting defect was found in twenty-six patients. It included observations of petechiae, easy bruising, hemorrhage, and abnormal platelet counts with significant thrombocythemia and thrombocytopensia. In thirty patients a battery of studies of coagulation revealed significant abnormalities in nine patients.

Based on this direct and indirect evidence we regard femoral-head necrosis as a skeletal expression of systemic disease which by a constellations of events alters coagulation homeostasis resulting in sludging, thrombosis, or hemorrhage in an area of susceptible blood supply.