What are the risk factors and symptoms of hip osteonecrosis?

Hip Osteonecrosis: Risk Factors and Symptoms

Hip osteonecrosis is bone death from inadequate vascular supply that most commonly affects adults in their third to fifth decades of life, presenting with hip pain as the primary symptom, and progresses to articular collapse and secondary osteoarthritis if untreated. 1

Risk Factors

Traumatic and Atraumatic Causes

The American College of Radiology identifies numerous risk factors that clinicians must screen for 1:

Medication-Related:

• Corticosteroid therapy (one of the most common causes) 1, 2
• Chemotherapy 1
• Radiation therapy 1

Substance Use:

• Alcohol consumption (major risk factor) 1, 2

Medical Conditions:

• HIV infection 1
• Lymphoma/leukemia 1
• Blood dyscrasias and coagulation abnormalities 1, 2
• Gaucher disease 1
• Caisson disease (decompression sickness) 1
• Hemoglobinopathies 1
• Hypercoagulability states 1
• Hyperlipidemia 1

Trauma:

• Direct hip trauma or fracture 1, 3

Prognostic Risk Factors

Once osteonecrosis develops, the American College of Radiology identifies additional factors that worsen outcomes 4, 5:

• Age >40 years 4, 5
• BMI >24 kg/m² 4, 5
• Joint effusion 4, 5
• Increased bone marrow edema 4, 5

Clinical Symptoms

Primary Presentation

Hip pain is the cardinal symptom that prompts patients to seek medical attention 1, 6. The American College of Radiology emphasizes that early diagnosis is critical because symptoms indicate the disease process is already underway 1.

Pain Characteristics

• Pain typically localizes to the affected hip 6
• May involve the spine in some cases 1
• Progressive in nature, worsening as the disease advances 3, 7

Asymptomatic Disease

A critical pitfall: approximately 5% of HIV patients may have asymptomatic disease detected only on MRI 1. This underscores that absence of symptoms does not exclude osteonecrosis in high-risk patients.

Critical Clinical Considerations

Bilateral and Multifocal Disease

Nontraumatic osteonecrosis is bilateral in 70-80% of cases, requiring evaluation of both hips even when symptoms are unilateral 4, 5. Additionally, multifocal involvement can affect the knee, ankle, and shoulder 5.

Natural History and Urgency

The American College of Radiology emphasizes that early diagnosis is important to exclude other causes of pain and allow for possible early surgical prevention to prevent articular collapse and need for joint replacements 1. Epiphyseal osteonecrosis leads to subchondral fracture and secondary osteoarthritis, explaining the severe long-term consequences 1.

Lesion Size as Prognostic Indicator

Lesions involving <30% of the femoral head have <5% progression to collapse, while lesions >30% have 46-83% risk of progression 4, 5. This makes early detection and quantification essential for treatment planning.

Common Pitfalls to Avoid

• Do not rely on plain radiographs alone for early diagnosis - they are insensitive for early disease, and MRI is the gold standard 4, 3, 6
• Do not evaluate only the symptomatic hip - bilateral screening is mandatory given the 70-80% bilateral involvement rate 4, 5
• Do not dismiss hip pain in patients with known risk factors (corticosteroid use, alcohol use, HIV) - these patients require aggressive workup 1
• Do not assume absence of symptoms means absence of disease in high-risk populations, particularly HIV patients where 5% have asymptomatic MRI findings 1