Snapshot A 54-year-old woman presents with right groin and buttock pain. She denies any recent history of trauma or fall on the affected area. Medical history is significant for multiple sclerosis (MS) that required systemic steroids due to a MS exacerbation. On physical exam, there is decreased passive and active range of motion of the hip. Magnetic resonance imaging demonstrates serpiginous peripheral sclerosis with inner granulation tissue. Introduction Clinical definition reduced vascular supply to the bone resulting in progressive and painful degeneration of the bone also termed osteonecrosis Epidemiology Incidence typically occurs in the anterolateral femoral head Demographics dependent on the cause of osteonecrosis e.g., systemic lupus erythematosus associated with osteonecrosis is more likely to be seen in women Etiology Pathogenesis impaired blood supply leads to infarction of the associated bone and bone marrow vascular insufficiency can result form mechanical blood vessel injury blood vessel compression venous occlusion thromboembolism Traumatic fractures e.g., femoral head, femur, and scaphoid bone dislocation e.g., slipped capital femoral epiphysis Atraumatic idiopathic (Legg-Calve-Perthes disease) alcohol use corticosteroids think of disorders that use corticosteroids such as systemic lupus erythematosus acute lymphoblastic leukemia transplantation Gaucher disease sickle cell disease caisson disease ("the bends") bisphosphonate therapy Presentation Symptoms asymptomatic seen in a small portion of patients pain groin pain suggests osteonecrosis of the femoral head thigh and buttock pain is also suggestive pain in weight bearing joints pain can occur at rest and at night Physical exam non-specific limited passive and active range of motion of the hip joint with hip involvement a limp can be seen Imaging Radiographs indication perform in patients with a clinical presentation concerning for osteonecrosis Magnetic resonance imaging (MRI) indication gold-standard for the diagnosis of osteonecrosis modalities without contrast Studies Making the diagnosis based on clinical presentation and imaging findings Differential Stress fracture Degenerative joint disease Treatment Management approach to preserve the native joint as long as possible treatment modalities are dependent on the location and extent of disease Complications Collapse of femoral head in cases of femoral involvement Degenerative joint disease Focal osteoporosis Prognosis Dependent on the extent of the lesion