['To investigate the early stages in the formation of bony spurs in relation to normal enthesis development.', "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.", '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.'] Does the mechanism of formation of bony spur ( enthesophytes ) in the achilles tendon?