Front X-ray of right knee of an adolescent (epiphyseal plates are open): arrows point to avascular necrosis and developing osteochondritis dissecans in the outer medial condyle of femur In the early stages, bone scintigraphy and MRI are the preferred diagnostic tools. X-ray images of avascular necrosis in the early stages usually appear normal. In later stages it appears relatively more radio-opaque due to the nearby living bone becoming resorbed secondary to reactive hyperemia. The necrotic bone itself does not show increased radiographic opacity, as dead bone cannot undergo bone resorption which is carried out by living osteoclasts. Late radiographic signs also include a radiolucency area following the collapse of subchondral bone (crescent sign) and ringed regions of radiodensity resulting from saponification and calcification of marrow fat following medullary infarcts. File:Osteonecrosis humerus 1.Radiography of total avascular necrosis of right humeral head. Woman of 81 years with diabetes of long evolution. File:Osteonecrosis femur 1.Radiography of avascular necrosis of left femoral head. Man of 45 years with AIDS. File:Osteonecrosis femur 2img.Nuclear magnetic resonance of avascular necrosis of left femoral head. Man of 45 years with AIDS. File:Intravertebral vacuum cleft sign.The intravertebral vacuum cleft sign (at white arrow) is a sign of avascular necrosis. Avascular necrosis of a vertebral body after a vertebral compression<unk>  is called Kümmel's disease. File:Pathology of avascular necrosis.Pathology of avascular necrosis, with a photograph of a cross-section of the involved bone at top left. The reactive zone shows irregular trebaculae with empty lacunae, and fibrosis of the marrow space. Types When AVN affects the scaphoid bone, it is known as Preiser disease. Another named form of AVN is Köhler disease, which affects the navicular bone of the foot, primarily in children. Yet another form of AVN is Kienböck's disease, which affects the lunate bone in the wrist.
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