title: The medial synovial fold of the posterior cruciate ligament: cadaveric investigation together with magnetic resonance imaging and histology.
abstract: OBJECTIVE
  The purposes of our study were to analyze magnetic resonance imaging (MRI) and cadaveric findings concerning the medial synovial fold of the posterior cruciate ligament (PCL) and to classify the types of fold according to anatomic location.
  
  
  METHODS
  Two musculoskeletal radiologists reviewed MR images of 17 cadaveric knees to classify the types of medial fold of the PCL by consensus. The MRI types were divided into 3 groups. In type A, there was no definitive medial fold; and in type B, inferior-short type, there was a small protrusion of the medial border. Type C, inferior-long type, had a long enough fold to exceed the imaginary line, which is connecting between the medial tibial condyle and posterolateral aspect of the medial femoral condyle. Correlations were sought between the findings derived from the MRI studies and cadaveric dissections. Histologic analyses of the medial fold were also performed.
  
  
  RESULTS
  On MRI, the most common type of medial fold was type B (76.4%), followed by type C (11.8%) and type A (11.8%). In the cadaveric investigation, the medial folds of both types B and C were found to project into the medial femorotibial joint. Moreover, there was also a protruding medial fold at the superior aspect of the PCL in the A. Histologic examination of the medial folds revealed collagenous tissue surrounded by synovial cells.
  
  
  CONCLUSIONS
  Medial folds of the PCL are normal synovial structures that can be seen by MRI and in cadaveric studies in a large proportion of the population.
authors.affiliation: From the Departments of *Radiology, †Orthopaedic Surgery, and ‡Anatomy and Cell Biology, Hanyang University Seoul Hospital, Korea; §Department of Pathology, National Police Hospital, Seoul, Korea.
authors.forename: Mimi
authors.initials: M
authors.lastname: Kim
authors.forename: Seunghun
authors.initials: S
authors.lastname: Lee
authors.forename: Bong Gun
authors.initials: BG
authors.lastname: Lee
authors.forename: Doo-Jin
authors.initials: DJ
authors.lastname: Paik
authors.forename: Jiyoon
authors.initials: J
authors.lastname: Bae
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology* / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008859:Microscopy, Polarization / Q000379:methods; D008875:Middle Aged; D015588:Observer Variation; D016119:Posterior Cruciate Ligament / Q000033:anatomy & histology* / Q000648:ultrastructure; D013583:Synovial Membrane / Q000033:anatomy & histology* / Q000648:ultrastructure