Osteonecrosis/avascular necrosis/aseptic necrosis:
Focal necrosis/death of bone (osteocytes) and bone marrow – related to ischaemia. Most commonly femoral head. In foot – talus, navicular and metatarsals are most commonly affected.
Traumatic disruption of blood supply; corticosteroid use (50% of nontraumatic cases) haemoglobinopathies; Cushing’s disease; renal transplant; pancreatitis; alcoholism; collagen disorders (eg SLE); thermal injuries; hyperuricaemia
Pain – often sudden onset – exacerbated by weightbearing – may be present at rest.
Tender to palpation; normal joint range of motion