title: Histologic findings and possible causes of osteochondritis dissecans of the knee.
abstract: BACKGROUND
  The histologic findings of osteochondritis dissecans of the knee vary widely, leading to differences in the interpretation of its origins. Hypothesis The differences in the histologic findings of osteochondritis dissecans might represent a course of pathologic progression.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Twelve knees in 11 patients (average age, 16 years) with osteochondritis dissecans of the medial femoral condyle were treated by biological internal fixation. During the surgery, cylinder osteochondral plugs were taken from the center of the osteochondritis dissecans lesion and examined with light microscopy.
  
  
  RESULTS
  A complete or partial cleft separated the specimens into 2 parts: basal and fragment sides. The surface of the basal side was covered with dense fibrous or cartilaginous tissue and active bone remodeling was found beneath the surface. In the fragment side, the deep surface was also covered with dense fibrous or cartilaginous tissue and the articular surface consisted of normal articular cartilage. The area between these 2 surfaces could be classified into 3 types: (1) necrotic subchondral trabeculae, (2) viable subchondral trabeculae, and (3) cartilage without bone trabeculae.
  
  
  CONCLUSIONS
  Based on the histologic findings of this study, the following origins and the pathologic progression of osteochondritis dissecans might be assumed: the initial change in the subchondral area is bone necrosis or subchondral fracture; the necrotic bone is then absorbed and replaced either by viable subchondral trabeculae or cartilage without bone trabeculae.
  
  
  CONCLUSIONS
  The results of this histologic study provide readers with several insights about the causes and treatment options of osteochondritis dissecans.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, 1-1 Seiryomachi, Aoba-ku, Sendai City, 980-8574, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Uozumi
authors.forename: Takehiko
authors.initials: T
authors.lastname: Sugita
authors.forename: Toshimi
authors.initials: T
authors.lastname: Aizawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takahashi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ohnuma
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000293:Adolescent; D002358:Cartilage, Articular / Q000473:pathology*; D002648:Child; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D010008:Osteochondritis Dissecans / Q000209:etiology* / Q000473:pathology; D055815:Young Adult