Front X-ray of right knee of an adolescent (epiphyseal plates are open): arrows point to<unk>  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<unk>  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<unk>  of right humeral head. Woman of 81 years with diabetes of long evolution. File:Osteonecrosis femur 1.Radiography of<unk>  of left femoral head. Man of 45 years with AIDS. File:Osteonecrosis femur 2img.Nuclear magnetic resonance of<unk>  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<unk> .<unk>  of a vertebral body after a vertebral compression fracture is called Kümmel's disease. File:Pathology of<unk> .Pathology of<unk> , 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<unk>  affects the scaphoid bone, it is known as Preiser disease. Another named form of<unk>  is Köhler disease, which affects the navicular bone of the foot, primarily in children. Yet another form of<unk>  is Kienböck's disease, which affects the lunate bone in the wrist.
Avascular necrosis
Legg–Calvé–Perthes disease
Acral necrosis
Osteopetrosis
Dysbaric osteonecrosis
Rheumatoid arthritis
Osteoradionecrosis
Sickle cell disease