We believe that all bone necrosis passes through a preradiologic stage, which is either painful and therefore Stage I or asymptomatic and therefore Stage O. Moreover, the diagnosis of osteonecrosis cannot be made by standard x-ray technique, which means that a normal x-ray examination does not guarantee that the hip is normal. The diagnosis in the early stage can be made only through the functional exploration of bone. In spite of multiple etiologies, there exists a pathophysiologic unity that centers around the circulatory disorder and is dominated by stasis. We believe that this explains the clinical and radiologic similarity of diverse causes of ischemic necrosis of bone. The medical treatment, preventive or prophylactic, is based on the causes and therefore is specific to the etiology of the avascular necrosis, whether that be cessation of drinking alcohol or reduction of steroid therapy. The interruptive treatment, however, which aborts the progression of the disease, rests on early diagnosis and core decompression. This dependence of results of treatment on timing has also been borne out by other authors as well, including Hungerford and Zizic and Marcus et al.