title: Diseases of Subchondral Bone 2.
abstract: Osteonecrosis of the knee can be divided into the following 3 categories: primary or Spontaneous osteonecrosis of the knee (SONK), secondary osteonecrosis (ON), and postarthroscopic osteonecrosis. Patient characteristics as well as underlying risk factors can help categorize the type of osteonecrosis and guide treatment. SONK was &filig;rst described by Ahlback et al in 1968. It is described as a disease of subchondral bone that leads to focal ischemia and bone marrow edema, necrosis, and possible subsequent structural collapse. SONK typically presents in the older women with frequent involvement of the medial femoral condyle. Secondary osteonecrosis is typically present in patients below 55 years of age. Unlike SONK, secondary ON presents multiple foci of bone marrow involvement with extension into the metaphysis and diaphysis. Postarthroscopic ON has been described after arthroscopic meniscectomy, shaver-assisted chondroplasty, anterior cruciate ligament reconstruction, and laser or radiofrequency-assisted debridement.
authors.affiliation: *Cedars-Sinai Medical Center †Kerlan Jobe Orthopedics at Cedars-Sinai, Los Angeles ‡Santa Monica Orthopaedic and Sports Medicine Group, Santa Monica, CA.
authors.forename: Frantz
authors.initials: F
authors.lastname: Lerebours
authors.forename: Neal S
authors.initials: NS
authors.lastname: ElAttrache
authors.forename: Bert
authors.initials: B
authors.lastname: Mandelbaum
mesh_terms: D001182:Arthroscopy / Q000009:adverse effects; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D010020:Osteonecrosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery*; D016059:Range of Motion, Articular; D012307:Risk Factors