title: A new arthroscopic classification of degenerative medial meniscus root tear that correlates with meniscus extrusion on magnetic resonance imaging.
abstract: BACKGROUND
  To determine a new classification system for medial meniscus root tears (MMRT) based on arthroscopic findings.
  
  
  METHODS
  24 knees (55%) belonged to the nondisplaced or overlapped group, and 20 knees (45%) to the widely displaced group. Absolute meniscal extrusion was defined as distance between outer edge of the articular cartilage of tibial plateau and meniscal outer edge. Relative extrusion was defined as extruded meniscus width divided by entire meniscal width, multiplied by 100. The proportion of knees with major (>3 mm) extrusion were compared in two groups, as were the severity of chondral wear and osteoarthritic change.
  
  
  RESULTS
  Absolute (4.6 mm vs. 3.7 mm, P=0.006) and relative (46% vs. 39%, P=0.042) extrusion of the medial meniscus were greater in widely displaced than in nondisplaced or overlapped group. Medial joint space width was significantly narrower in the widely displaced than in the nondisplaced or overlapped group (3.0 mm vs. 4.0 mm, P=0.007). The widely displaced group had a 4° greater varus deformity, and higher rates of major extrusion (>3 mm), grade III or IV chondral wear in the medial femoral condyle (60% vs. 29%, P=0.039) and medial compartment osteoarthritis (75% vs. 21%, P=0.001) than did the nondisplaced or overlapped group.
  
  
  CONCLUSIONS
  Widely displaced MMRT had greater meniscal extrusion and more severe chondral wear and osteoarthritis than did nondisplaced or overlapped MMRT. In this novel classification system, the stage of MMRT severity was associated with tear site displacement.
  
  
  METHODS
  Case series (level IV).
authors.affiliation: Department of Orthopedic Surgery, University of Ulsan, College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
authors.forename: Seong-Il
authors.initials: SI
authors.lastname: Bin
authors.affiliation: Department of Orthopaedic Surgery, Korea University, College of medicine, Anam Hospital, Seoul, Republic of Korea.
authors.forename: Tae-Wan
authors.initials: TW
authors.lastname: Jeong
authors.affiliation: Department of Emergency Medicine, Korea University, College of medicine, Anam Hospital, Seoul, Republic of Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: eoak22@empal.com.
authors.forename: Dae-Hee
authors.initials: DH
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D001182:Arthroscopy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging*; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012421:Rupture / Q000145:classification / Q000175:diagnosis; D000070600:Tibial Meniscus Injuries / Q000145:classification* / Q000175:diagnosis; D013997:Time Factors
keywords: Arthroscopy; Displacement; Extrusion; Medial meniscus; Root tear