title: MRI injury patterns in surgically confirmed and reconstructed posterolateral corner knee injuries.
abstract: OBJECTIVE
  The posterolateral corner (PLC) of the knee is anatomically complex with similarly complex MR imaging findings in acutely injured knees. The purpose of this study was to define the MRI pattern of injury in cases of PLC disruption requiring surgery because of clinical instability.
  
  
  METHODS
  The knee MRIs of 22 patients who underwent surgical repair and/or reconstruction of PLC injury were retrospectively reviewed. The fibular collateral ligament (FCL), popliteus tendon (PT), biceps femoris (BF), popliteofibular ligament (PFL), arcuate ligament (AL), and fabellofibular ligament (FFL) were evaluated and graded as follows: complete tear, high-grade partial tear, low-grade partial tear, and normal.
  
  
  RESULTS
  In the 22 cases of PLC injury that necessitated surgery, a constellation of findings involving the larger structures of the PLC was identified. Of the FCL, PT, and BF (considered larger structures), at least two were abnormal in all 22 injury cases. Of the PFL, AL, and FFL (considered smaller structures), the PFL appeared abnormal in 19 cases, yet neither the AL nor FFL were confidently characterized in the injury group.
  
  
  CONCLUSIONS
  The larger structures of the PLC are easily evaluated using standard MRI techniques. This study identified a predictable pattern of imaging findings involving these more easily assessed structures in those patients who were felt to be clinically unstable and underwent surgical reconstruction, as at least two were abnormal in all 22 cases. The smaller structures of the PLC are difficult to assess with MRI; however, direct visualization of their involvement on MRI is not necessary to report a clinically unstable PLC injury. Emphasis of this simplified but critical analysis of the FCL, BF and PT on MRI scans reviewed by radiologists and orthopaedic surgeons may help to prevent delayed diagnosis of unstable PLC injuries.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. Collins.Mark@Mayo.edu.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Collins
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. Bond.Jeffery@Mayo.edu.
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Bond
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. Crush.Andrew@Mayo.edu.
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Crush
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. Stuart.Michael@Mayo.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Stuart
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. King.Alexander@Mayo.edu.
authors.forename: Alexander H
authors.initials: AH
authors.lastname: King
authors.affiliation: Department of Orthopedic Surgery and Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN, 55905, USA. Levy.Bruce@Mayo.edu.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Levy
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000473:pathology* / Q000601:surgery*; D008023:Ligaments, Articular / Q000293:injuries* / Q000473:pathology* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013708:Tendon Injuries / Q000473:pathology* / Q000601:surgery; D055815:Young Adult
keywords: Instability; MRI; Posterolateral corner injury