What are the typical signs and symptoms of avascular necrosis (AVN) of the femoral head?

Signs and Symptoms of Avascular Necrosis of the Femoral Head

The hallmark presentation of femoral head AVN is hip pain that is often insidious, progressive, and may initially manifest as low back or buttock pain, particularly at night, with restricted hip range of motion—especially internal rotation and abduction—being the key objective finding on examination. 1

Clinical Presentation Algorithm

Symptomatic Presentation

• Pain characteristics:

  • Dull, constant ache that sharpens with weight-bearing activities 2
  • Often deceptively localized to the lumbosacral area and buttocks rather than the hip itself 3
  • Nocturnal pain is particularly characteristic 3
  • Progressive over weeks to months 2

• Functional impairment:

  • Antalgic gait (limping) 2
  • Limited range of motion, particularly in the final phases of hip movement 3
  • Stiffness and disability in daily activities 4

Physical Examination Findings

The most critical objective finding is asymmetric limitation of hip range of motion, specifically:

• Restricted internal rotation (most sensitive early finding) 3
• Limited abduction 3
• Positive orthopedic provocation tests 2
• Even slight limitation warrants immediate imaging 3

Critical Clinical Pitfalls

The Deceptive Presentation Problem

A major diagnostic trap: 20.9% of AVN patients are initially misdiagnosed and treated by neurologists/neurosurgeons for presumed spinal pathology 3. This occurs because:

• Pain commonly radiates to the lower back and buttocks
• Patients may present with pseudoradicular signs
• The hip is not examined systematically
• Four patients in one series underwent unnecessary discectomies before AVN was diagnosed 3

To avoid this error: Examination of hip range of motion is mandatory in ANY patient presenting with low back or buttock pain 3.

The Asymptomatic Phase

Many patients, particularly those with metadiaphyseal involvement, remain completely asymptomatic 1. This means:

• True prevalence is vastly underestimated 1
• Incidental findings on CT scans performed for other reasons are common 1
• In nontraumatic cases, bilateral involvement occurs in 70-80% of patients 1, necessitating bilateral screening even when symptoms are unilateral

Disease Progression and Timing

Early Stage (Pre-radiographic)

• Pain may be the only symptom
• Normal plain radiographs 5, 6
• Subtle restriction of hip motion is the key physical finding
• This is when diagnosis is most critical for joint preservation 1

Advanced Stage (Post-collapse)

• Severe pain with weight-bearing
• Marked limitation of all hip movements
• Subchondral fracture has occurred
• Secondary osteoarthritis develops 1
• At this stage, only total hip arthroplasty remains effective 3

Associated Risk Factors to Elicit in History

When AVN is suspected, specifically inquire about 1:

• Corticosteroid therapy (dose and duration)
• Alcohol use (chronic abuse)
• HIV infection
• Hematologic malignancies (lymphoma/leukemia)
• Blood dyscrasias (sickle cell disease)
• Prior chemotherapy or radiation
• Trauma history
• Gaucher disease
• Diving history (Caisson disease)

Multifocal Involvement Pattern

When femoral head AVN is diagnosed, systematically screen other sites 1:

• Contralateral hip (70-80% bilateral) 1
• Knee (44% in steroid users) 1
• Shoulder (15% in steroid users) 1
• Ankle (17% in steroid users) 1

Diagnostic Imperative

The diagnosis is ultimately one of exclusion requiring imaging confirmation 6. However, the clinical presentation—particularly the combination of nocturnal hip/buttock pain with restricted internal rotation—should trigger immediate suspicion and prompt MRI evaluation, as early diagnosis is the only opportunity to preserve the native joint and avoid total hip replacement 1.