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Members' feedback

"I'm finding it shocking and surprising the number of new people joining the community. Let me explain. I was diagnosed with AVN first in both knees back in 2005, over the next few years it was found in both hips and shoulders. I had never come across AVN before and felt like I was the only person with it, I was always having to explain to people what it was."
 
"Thankfully I found this website and community over a year ago and realised I was not the only one suffering with AVN, it has been such a help talking to fellow sufferers who understand what I am going through."
 
Text taken from a recent post in our community forum.

Join us

If you are suffering from avascular necrosis AVN Osteonecrosis ON, or are close to someone that is, please consider joining our AVN Charity UK community. You will find many shared experiences about AVN and how it affects each of us differently, importantly there are also excellent success stories about the road to "Pain Free".
 
We also welcome any health professionals who are involved in any way with Avascular Necrosis AVN, please let us know how you think you can help.

Anatomy of the kneeAnatomy of the kneeAvascular necrosis AVN of the Knee

In the knee, there are two types of avascular necrosis AVN or osteonecrosis:
1. Spontaneous Osteonecrosis of the Knee (SPONK)
2. Secondary Osteonecrosis or AVN Avascular Necrosis

Anatomy of the knee

Our knee is the most complicated and largest joint in our body. It is also the most vulnerable because it bears enormous weight and pressure loads while providing flexible movement. When we walk, our knees support 1.5 times our body weight; climbing stairs is about 3-4 times our body weight and squatting about 8 times.

The knee joint is synovial (having fluid filled cushioning pouches or sacs found in spaces between tendons, ligaments and bones) found in the area of joints.

The knee is part of a chain that includes the pelvis, hip, and upper leg above, and the lower leg, ankle and foot below. All of these work together and depend on each other for function and movement.

The knee joint bears most of the weight of the body. When we’re sitting, the tibia and femur barely touch; standing they lock together to form a stable unit.

Spontaneous Osteonecrosis of the Knee SPONK

SPONK is poorly understood but seems to be the result of some type of trauma to the knee. This trauma may be minor or severe. It usually affects only one knee and most often a single area within the knee. The area of bone in the knee loses its normal blood supply and may eventually weaken and collapse. This typically leads to pain and functional limitations. The pain is often sudden onset and increases with weight bearing, stair climbing, and at night. SPONK is most often seen in elderly women with osteoporosis. When collapse has occurred, surgical intervention is often necessary. Total or partial knee replacement can provide dramatic improvement in pain, joint function, and quality of life.

MRI images show (A) Sagittal T1 weighted MRI showing a low signal subchondral lesion (arrows) of linear morphology. This lesion is associated with ill defined bone marrow oedema. (B) On T2 weighted sequences the subchondral lesion also shows a low signal (arrowheads) and the ill defined bone marrow oedema shows a high signal. Joint effusion (arrows) is also well demonstrated, with a homogeneous high signal. Click on image to see much larger view.MRI images show (A) Sagittal T1 weighted MRI showing a low signal subchondral lesion (arrows) of linear morphology. This lesion is associated with ill defined bone marrow oedema. (B) On T2 weighted sequences the subchondral lesion also shows a low signal (arrowheads) and the ill defined bone marrow oedema shows a high signal. Joint effusion (arrows) is also well demonstrated, with a homogeneous high signal. Click on image to see much larger view.SPONK Possible misnomer

Originally it was understood that this was caused by bone death, however recent surveys suggest that sufferers have a different history, clinical course and bony involvement than those with true AVN. AVN typically  occurring in much younger patients (less than 40 years) often affecting multiple joints and condyles, and is associated with known risk factors such as corticosteroids and alcohol abuse.

SPONK typically affects the medial condyle or inner side of the knee, it is unilateral (one knee not both) and typically occurs in older patients with no AVN risk factors.

Microscopic examination of SPONK lesions were originally thought to be signs of bone death. Recent work has shown that the cause of SPONK may be attributed to subchondral or stress fractures in bone that has lower bone density (Osteopenia).

Possibly SPONK may  be a misnomer, and not true AVN - this has yet to be confirmed.

Secondary Avascular Necrosis AVN

The cause of secondary AVN or osteonecrosis is unknown. However, several risk factors are associated with the disease. Corticosteroid use (such as oral prednisolone) is the most significant risk factor.

Other risk factors include alcohol abuse, sickle cell disease, systemic lupus erythematosus (SLE), caisson disease (barotrauma), and Gaucher disease. Multiple areas of the knee are often affected, and 80% of people have both knees affected.

Other areas of the body (such as the hip) also may be affected. The pain is usually longstanding and insidious in nature. When joint collapse has occurred, surgical intervention is often necessary.

Total knee replacement (TKR) can provide dramatic improvement in pain, joint function, and quality of life.

Image notes

Sagittal T1 and T2 weighted refers to MRI image signal intensity, allowing the radiographer and surgeon to interpret the image in a useful way.

Last Updated on Thursday, 01 January 2015 20:57