title: Evaluation of the morphological variations of the meniscus: a cadaver study.
abstract: OBJECTIVE
  The purpose of this study was to reveal the prevalence of the subtypes of the meniscus using human cadaver knees.
  
  
  METHODS
  Four hundred and thirty-seven cadaveric knees in 219 subjects (formalin fixed, Japanese population) with a median age of 83 years (54-97) were included in this study. All soft tissues surrounding the knee, excluding the meniscus, were resected, and macroscopic assessment of the meniscus was performed. Meniscus subtypes were classified as: (1) normal meniscus, (2) complete discoid, (3) incomplete discoid, (4) ring-shaped, and (5) double-layered.
  
  
  RESULTS
  All subtypes of the meniscus were observed in the lateral meniscus. Complete discoid lateral meniscus was observed in 27 knees (6.2%), incomplete discoid lateral meniscus was observed in 139 knees (31.8%), ring-shaped lateral meniscus was observed in 4 knees (0.9%), and double-layered meniscus was observed in 2 knees (0.5%).
  
  
  CONCLUSIONS
  This study reports the accurate prevalence of ring-shaped and double-layered meniscus. None of the subtypes were detected in the medial meniscus in this study. For clinical relevance, the results of this study can be useful in assisting the diagnosis of meniscus tear in clinical situations.
authors.affiliation: Department of Orthopedic Surgery, Surugadai Nihon University Hospital, Chiyodaku Kanda Surugadai 1-8-13, Tokyo, Japan, keinosukeryu@yahoo.co.jp.
authors.forename: Keinosuke
authors.initials: K
authors.lastname: Ryu
authors.forename: Takanori
authors.initials: T
authors.lastname: Iriuchishima
authors.forename: Midori
authors.initials: M
authors.lastname: Oshida
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Saito
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kato
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Tokuhashi
authors.forename: Shin
authors.initials: S
authors.lastname: Aizawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D002102:Cadaver; D005260:Female; D006801:Humans; D007564:Japan; D007719:Knee Joint / Q000033:anatomy & histology*; D008297:Male; D008592:Menisci, Tibial / Q000033:anatomy & histology*; D008875:Middle Aged; D012737:Sex Factors