title: The mechanism of formation of bony spurs (enthesophytes) in the achilles tendon.
abstract: OBJECTIVE
  To investigate the early stages in the formation of bony spurs in relation to normal enthesis development.
  
  
  METHODS
  Histologic sections of rat Achilles tendons, stained with toluidine blue or Masson's trichrome, were examined in animals ranging from 2 weeks to 1 year of age. Further material prepared for immunohistochemistry was labeled with monoclonal antibodies for laminin and type IV collagen to highlight the presence of small blood vessels at the enthesis. Sections of small spurs from the Achilles tendons of elderly humans were also examined for comparison.
  
  
  RESULTS
  As a part of normal development, bone grows into the Achilles tendon as the calcaneus enlarges. Ossification is preceded by vascular invasion, which occurs along rows of enthesis fibrocartilage cells. Small bony spurs develop when ossification at one point on the enthesis outstrips that on either side.
  
  
  CONCLUSIONS
  Bony spurs can develop in the Achilles tendon without the need for preceding microtears or any inflammatory reaction, and they form by endochondral ossification of enthesis fibrocartilage. The increased surface area created at the tendon-bone junction may be an adaptive mechanism to ensure the integrity of the interface in response to increased mechanical loads.
authors.affiliation: School of Biosciences, Cardiff University, UK.
authors.forename: M
authors.initials: M
authors.lastname: Benjamin
authors.forename: A
authors.initials: A
authors.lastname: Rufai
authors.forename: J R
authors.initials: JR
authors.lastname: Ralphs
mesh_terms: D000125:Achilles Tendon / Q000473:pathology*; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000906:Antibodies / Q000032:analysis; D003094:Collagen / Q000276:immunology; D005096:Exostoses / Q000209:etiology*; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000906:Antibodies; D003094:Collagen