Imaging of Musculoskeletal Disorders
Avascular necrosis

Key features

  • Initial X-ray may be normal
  • Geographic lines
  • Subsidence, flattening and destruction of joint surface

Avascular necrosis (AVN), also known as osteonecrosis, is most common in the femoral head. In early disease the X-ray can be normal, and MRI may be required if the diagnosis is suspected clinically.

AVN femoral head - MRI (T1 image - fat sensitive image)

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AVN femoral head - MRI (T1 image - fat sensitive image)

  • Plain X-ray was normal in this patient
  • The MRI shows a geographic line of low signal which passes across the femoral head deep to the weight-bearing articular surface
  • (Same patient as image below)

AVN femoral head - MRI (STIR image - water sensitive image)

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AVN femoral head - MRI (STIR image - water sensitive image)

  • (Same patient as image above)
  • This MRI image shows the same line is made up of two layers
  • The white line indicates oedema within a layer of granulation tissue and the black line indicates bone sclerosis
  • This ‘double line sign’ is a classic feature of AVN

AVN - Plain X-ray

As AVN develops, it becomes visible on a plain X-ray.

AVN femoral head – X-ray

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AVN femoral head – X-ray

  • A lucent geographic line undermines the articular weight-bearing surface of the femoral head
  • The femoral head articular surface subsides and is flattened
  • (Same patient as image below)

As AVN progresses, the femoral head may be destroyed, and secondary changes of the acetabular surface may become visible.

Advanced AVN femoral head – X-ray

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Advanced AVN femoral head – X-ray

  • (Same patient as image above)
  • The femoral head articular surface has been destroyed
  • The cortex of the acetabulum articular surface is thinned and flattened

AVN Eponyms

AVN most commonly affects the hips. Eponyms are attributed to AVN of some of the less common sites, for example AVN of the second metatarsal head can be referred to as 'Freiberg's infraction, and AVN of the lunate bone can be referred to as 'Keinbock's disease'.

Frieberg’s infraction

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Frieberg’s infraction

  • The articular surface of the distal phalanx of the second toe metatarsophalangeal joint appears flattened
  • Linear lucency and sclerosis passes across the metatarsal head and undermines the articular surface

Keinbock’s disease

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Keinbock’s disease

  • The lunate bone has become very sclerotic and is flattened in this patient with longstanding Keinbock's disease (AVN of the lunate bone)

Page author: Salisbury NHS Foundation Trust UK (Read bio)

Page edited by: Dr Richard Smith BSc MSc MBBS FRCP PGDip - Consultant Rheumatologist (Read bio)

Last reviewed: January 2020