Subchondral insufficiency fracture of the knee: review of current concepts and radiological differential diagnoses

Junko Ochi, Taiki Nozaki, Akimoto Nimura, Takehiko Yamaguchi, Nobuto Kitamura

Research output: Contribution to journalReview articlepeer-review

24 Citations (Scopus)


Subchondral insufficiency fracture of the knee (SIFK) is a common cause of knee joint pain in older adults. SIFK is a type of stress fracture that occurs when repetitive and excessive stress is applied to the subchondral bone. If the fracture does not heal, the lesion develops into osteonecrosis and results in osteochondral collapse, requiring surgical management. Because of these clinical features, SIFK was initially termed “spontaneous osteonecrosis of the knee (SONK)” in the pre-MRI era. SONK is now categorized as an advanced SIFK lesion in the spectrum of this disease, and some authors believe the term “SONK” is a misnomer. MRI plays a significant role in the early diagnosis of SIFK. A subchondral T2 hypointense line of the affected condyle with extended bone marrow edema-like signal intensity are characteristic findings on MRI. The large lesion size and the presence of osteochondral collapse on imaging are associated with an increased risk of osteoarthritis. However, bone marrow edema-like signal intensity and osteochondral collapse alone are not specific to SIFK, and other osteochondral lesions, including avascular necrosis, osteochondral dissecans, and osteoarthritis should be considered. Chondral lesions and meniscal abnormalities, including posterior root tears, are also found in many patients with SIFK, and they are considered to be related to the development of SIFK. We review the clinical and imaging findings, including the anatomy and terminology history of SIFK, as well as its differential diagnoses. Radiologists should be familiar with these imaging features and clinical presentations for appropriate management.

Original languageEnglish
Pages (from-to)443-457
Number of pages15
JournalJapanese Journal of Radiology
Issue number5
Publication statusPublished - 2022 May
Externally publishedYes


  • Meniscal root tear
  • Spontaneous osteonecrosis of the knee
  • Subchondral insufficiency fracture
  • Subchondral plate

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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