Causes of pain in early and advanced stage osteonecrosis

The natural history, pathophysiology, and etiology of pain in nontraumatic osteonecrosis (ON) are poorly understood. In most clinical scenarios, a patient presents with pain which then leads to imaging examinations that identify the ON. Therefore, it is diffi cult to determine the frequency of asymptomatic disease. Nonetheless, it is clear that asymptomatic disease occurs as it is often identifi ed incidentally, either in a contralateral site or when imaging is performed for unrelated reasons.