Nontraumatic Osteonecrosis of the Femoral Head: An Update

&#x27a2; Nontraumatic osteonecrosis of the femoral head should be suspected in patients who are <50 years of age who have persistent hip pain despite normal radiographs.&#x27a2; Bilateral involvement is common; magnetic resonance imaging (MRI) of the contralateral hip is recommended.&#x27a2; MRI is the most sensitive modality for detecting early disease.&#x27a2; Femoral head sphericity is assessed on anteroposterior, lateral, and 30&#xba; view radiographs.&#x27a2; Small pre-collapse lesions have the best prognosis. Large lateral lesions and subchondral collapse predict rapid progression.&#x27a2; Systemic risk factors and multifocal disease should be actively evaluated.&#x27a2; Joint-preserving procedures are most effective before structural collapse.&#x27a2; Total hip arthroplasty remains the most reliable treatment after femoral head collapse.