title: The acutely ACL injured knee assessed by MRI: are large volume traumatic bone marrow lesions a sign of severe compression injury?
abstract: OBJECTIVE
  To map by magnetic resonance imaging (MRI) and quantitative MRI (qMRI) concomitant fractures and meniscal injuries, and location and volume of traumatic bone marrow lesions (BMLs) in the acutely anterior cruciate ligament (ACL) injured knee. To relate BML location and volume to cortical depression fractures, meniscal injuries and patient characteristics.
  
  
  METHODS
  One hundred and twenty-one subjects (26% women, mean age 26 years) with an ACL rupture to a previously un-injured knee were studied using a 1.5T MR imager within 3 weeks from trauma. Meniscal injuries and fractures were classified by type, size and location. BML location and volume were quantified using a multi-spectral image data set analyzed by computer software, edited by an expert radiologist.
  
  
  RESULTS
  Fractures were found in 73 (60%) knees. In 67 (92%) of these knees at least one cortical depression fracture was found. Uni-compartmental meniscal tears were found in 44 (36%) subjects and bi-compartmental in 24 (20%). One hundred and nineteen (98%) knees had at least one BML, all but four (97%) located in the lateral compartment. Knees with a cortical depression fracture had larger BML volumes (P<0.001) than knees without a cortical depression fracture, but no associations were found between meniscal tears and BML volume or fractures. Older age at injury was associated with smaller BML volumes (P<0.01).
  
  
  CONCLUSIONS
  A majority of the ACL injured knees had a cortical depression fracture, which was associated with larger BML volumes. This indicates strong compressive forces to the articular surface and cartilage at the time of injury, which may constitute an additional risk factor for later knee osteoarthritis development.
authors.affiliation: Department of Orthopedics, Clinical Sciences Lund, Lund University, Lund, Sweden. richard.frobell@med.lu.se
authors.forename: R B
authors.initials: RB
authors.lastname: Frobell
authors.forename: H P
authors.initials: HP
authors.lastname: Roos
authors.forename: E M
authors.initials: EM
authors.lastname: Roos
authors.forename: M-P
authors.initials: MP
authors.lastname: Hellio Le Graverand
authors.forename: R
authors.initials: R
authors.lastname: Buck
authors.forename: J
authors.initials: J
authors.lastname: Tamez-Pena
authors.forename: S
authors.initials: S
authors.lastname: Totterman
authors.forename: T
authors.initials: T
authors.lastname: Boegard
authors.forename: L S
authors.initials: LS
authors.lastname: Lohmander
mesh_terms: D000208:Acute Disease; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000175:diagnosis; D001853:Bone Marrow / Q000293:injuries* / Q000473:pathology; D005260:Female; D050723:Fractures, Bone / Q000175:diagnosis / Q000209:etiology; D006801:Humans; D007718:Knee Injuries / Q000175:diagnosis* / Q000209:etiology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D013314:Stress, Mechanical; D000070600:Tibial Meniscus Injuries