Avascular Necrosis – AVN (osteonecrosis, aseptic necrosis, bone infarction)

Avascular necrosis, also known as AVN or aseptic necrosis, is bone death (necrosis) due to a lack of blood supply (avascular) to a discrete area of bone. Osteonecrosis and bone infarctions are specific types of avascular necrosis. Osteonecrosis is a loss of blood supply in the bone immediately below the cartilage of a joint (subchondral bone). Whereas a bone infarction is a loss of blood supply in the shaft of the bone or an area of bone not near the joint. Fortunately, avascular necrosis is not common and many cases of AVN do not cause symptoms. However, for some patients the symptoms of AVN can be debilitating, and treatment can be challenging. There are a number of causes of AVN, and in many cases the exact cause is not known. Common causes include:

• Localized trauma, such as a fracture or joint dislocation.
• Blood conditions that cause increase blood clotting such as sickle cell anemia.
• Alcoholism 
• Corticosteroid use 
• Idiopathic -in many instances of avascular necrosis the exact cause is not identified

Avascular necrosis results from a loss of blood supply to a local area of bone. This loss of blood supply could occur due to disruption of a major artery (ex. secondary to a nearby fracture) leading to the bone; or from clotting up of some of the small arterioles supplying the bone with oxygenated blood. Certain bones are much more susceptible to avascular necrosis than others. Common areas of avascular necrosis include:

• The femoral head (the ball part of the ball and socket hip joint), particularly following a fracture to the femoral neck
• The talar body (the lower bone of the ankle joint). The talus generally has a tenuous blood supply as this bone is mostly covered with cartilage. Local trauma (ex. talar neck fracture) and conditions that cause thickening and increase clotting of the blood can predispose to the development of talar body AVN
• The femoral condyles of the knee (part of the upper bone of the knee joint) in a condition known as spontaneous osteonecrosis of the knee (SONK).
• The scaphoid bone of the wrist which is mostly covered with cartilage and therefore has a tenuous blood supply. This predisposes the scaphoid to develop avascular necrosis following certain scaphoid fractures.
• The lunate bone of the wrist which similar to the scaphoid is mostly covered with cartilage and can develop avascular necrosis in a condition called Kienbock’s disease.

Listen to a Podcast on Avascular Necrosis

Symptoms of Avascular Necrosis 

Many cases of AVN are asymptomatic and only show up on x-ray or MRI as an incidental finding. However, if the AVN causes collapse of the affected bone, the associated joint can become quite painful from localized arthritis. This has to do with how avascular necrosis progresses. When the blood supply is lost to an area of the bone, the bone in this area dies. However, that area of dead bone does not necessarily collapse as the existing architecture of the bone persists. However, once the affected area of bone has new blood vessels grow into the dead bone (revascularization) the bone will often weaken. If forces are placed through this area of bone while it is regaining its blood supply the weakened bone may collapse. If the bone adjacent to a joint collapses. This deformity of the joint will often lead to considerable arthritis and pain. As an example, the femoral head can lose its blood supply following a hip fracture involving the femoral neck. This type of hip fracture leads to death of part, or all, of the bone of the femoral head. This can cause localized discomfort. Increased discomfort will occur if the femoral head collapses leading to rapid hip arthritis.

Treatment of Avascular Necrosis

Treatment of an area of AVN varies widely depending upon:

• The amount of symptoms
• The location of the AVN
• The extent of the AVN
• Whether there has been collapse of the existing bone affected by AVN

Asymptomatic Avascular Necrosis

AVN that is identified incidentally on x-ray or MRI and is not associated with any pain often does not require any specific treatment. However, if the affected area produces mild symptoms, or the noted area of AVN is quite large, some treatment to protect the area until the blood supply has returned (revascularization) to the affected area of bone may be indicated. Unfortunately, complete revascularization of an area of AVN can take many months.

Symptomatic AVN without Collapse of the Bone

If the area of bone affected by the avascular necrosis creates symptoms of pain and discomfort, treatment is often required. The specific treatment will depend upon the affected bone, the extent of symptoms, and the recommendation of the treating physician. Treatment could include limiting loading and use of the affected area (ex. using a cast or walker boot, avoiding specific activities, etc.). Alternatively, if the area of a vascular bone is tenuous surgery may be recommended to: 

• Try and revascularized the area;
• Stabilize an associated fracture or;  
• Cut and reposition (osteotomy) nearby bones to change the loading forces through the area of AVN

Collapse of the Bone Affected by AVN with Resulting Arthritic Joint Pain

If the area affected by AVN is symptomatic and associated with collapse of the normal bony architecture a salvage surgical procedure maybe required. This often means a joint replacement or a joint fusion to help alleviate the pain from the affected arthritic joint.

Edited by Stephen Pinney MD, August 16th, 2026.