This site is targeted at medical and radiology professionals, contains user contributed content, and material that may be confusing to a lay audience. Use of this site implies acceptance of our Terms of Use.

Spontaneous osteonecrosis of the knee

Dr Ahmed Abd Rabou and Dr Frank Gaillard et al.

Spontaneous osteonecrosis of the knee, also known as Ahlback disease, SONK or even SPONK has similar appearances to osteochondritis dissecans of the knee but is found in an older age group.

Osteonecrosis in this setting has no predisposing factors. However, by definition, secondary osteonecrosis of the knee occurs secondary to an insult.

Epidemiology

SONK is seen more frequently in women (M:F 1:3), and affects older patients, typically over the age of 55.

Radiographic features

It is almost always unilateral, usually affects the medial femoral condyle and is often associated with a meniscal tear.

Prognosis

Can vary from complete recovery to total joint collapse ².

Differential diagnosis

osteochondritis dissecans of the knee

Etymology

It was first systematically described by Ahlback in 1968 ²

This article is a stub, which means it needs more content. You can contribute to Radiopaedia.org too. Just register and edit... every little bit helps.