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.
SONK is not caused by bone death but may be caused by osteoporosis and insufficiency fractures.6
SONK is seen more frequently in women (M:F 1:3), and affects older patients, typically over the age of 55.
It is almost always unilateral, usually affects the medial femoral condyle and is often associated with a meniscal tear.
Can vary from complete recovery to total joint collapse 2.
History and etymology
It was first systematically described by Ahlback in 1968 2
- 1. Takeda M, Higuchi H, Kimura M et-al. Spontaneous osteonecrosis of the knee: histopathological differences between early and progressive cases. J Bone Joint Surg Br. 2008;90 (3): 324-9. doi:10.1302/0301-620X.90B3.18629 - Pubmed citation
- 2. Björkengren AG, Alrowaih A, Lindstrand A et-al. Spontaneous osteonecrosis of the knee: value of MR imaging in determining prognosis. AJR Am J Roentgenol. 1990;154 (2): 331-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Fotiadou A, Karantanas A. Acute nontraumatic adult knee pain: the role of MR imaging. Radiol Med. 2009;114 (3): 437-47. doi:10.1007/s11547-009-0380-z - Pubmed citation
- 4. Ramnath RR, Kattapuram SV. MR appearance of SONK-like subchondral abnormalities in the adult knee: SONK redefined. Skeletal Radiol. 2004;33 (10): 575-81. doi:10.1007/s00256-004-0777-7 - Pubmed citation
- 5. Zywiel MG, Mcgrath MS, Seyler TM et-al. Osteonecrosis of the knee: a review of three disorders. Orthop. Clin. North Am. 2009;40 (2): 193-211. doi:10.1016/j.ocl.2008.10.010 - Pubmed citation
- 6. Mears SC, McCarthy EF, Jones LC et-al. Characterization and pathological characteristics of spontaneous osteonecrosis of the knee. Iowa Orthop J. 2010;29: 38-42. Free text at pubmed - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Spontaneous osteonecrosis of the knee (SONK)||✗|