title: MRI of bone marrow edema-like signal in the pathogenesis of subchondral cysts.
abstract: OBJECTIVE
  To determine if a relationship exists between bone marrow edema-like signal and subchondral cysts on magnetic resonance imaging (MRI).
  
  
  METHODS
  Retrospective cohort of 32 patients with two sequential knee MRI. Patients with acute trauma, infection, neoplasm, or osteonecrosis were excluded. The degree of osteoarthritis was assessed using an adaptation of the Baltimore Longitudinal Study of Aging (BLSA) scale. Initial and follow-up exams were reviewed for presence, location, size and changes of marrow edema-like signal, subarticular cysts and cartilage abnormality. All locations in the knee were aggregated for analysis with descriptive statistics.
  
  
  RESULTS
  The mean time interval between exams was 17.52 months (range 2.1-40.1 months). There were 23 cysts: 11 (47.8%) new, 6 (26.1%) increased size, 1 (4.4%) decreased size, and 5 (21.7%) no change in pre-existing lesions. Cysts always arose from regions of marrow edema-like signal. There were 68 subarticular areas of marrow edema-like signal: 16 (23.5%) new, 23 (33.8%) increased size, 17 (25%) decreased size, 11 (16.2%) resolved and 1 (1.5%) no change in pre-existing lesion. Marrow edema-like signal size always changed with cyst development: increased in 6/11 (54.5%), decreased in 2/11 (18.1%) and resolved in 3/11 (27.2%). Change in cyst size was always accompanied by a change in edema-like signal size. An MRI visible cartilage abnormality was adjacent to 87% (20/23) of cysts. The mean BLSA score changed from 2.6 to 3.6 indicating an overall progression of osteoarthritis.
  
  
  CONCLUSIONS
  Subchondral cysts develop in pre-existing regions of subchondral bone marrow edema-like signal.
authors.affiliation: Harvard Medical School, Department of Radiology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA. jcarrino@partners.org
authors.forename: J A
authors.initials: JA
authors.lastname: Carrino
authors.forename: J
authors.initials: J
authors.lastname: Blum
authors.forename: J A
authors.initials: JA
authors.lastname: Parellada
authors.forename: M E
authors.initials: ME
authors.lastname: Schweitzer
authors.forename: W B
authors.initials: WB
authors.lastname: Morrison
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001845:Bone Cysts / Q000175:diagnosis* / Q000209:etiology; D001853:Bone Marrow / Q000473:pathology; D004487:Edema / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000175:diagnosis*; D012189:Retrospective Studies