The mechanism of formation of bony spurs (enthesophytes) in the Achilles tendon
Article first published online: 2 APR 2001
Copyright © 2000 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 43, Issue 3, pages 576–583, March 2000
How to Cite
Benjamin, M., Rufai, A. and Ralphs, J. R. (2000), The mechanism of formation of bony spurs (enthesophytes) in the Achilles tendon. Arthritis & Rheumatism, 43: 576–583. doi: 10.1002/1529-0131(200003)43:3<576::AID-ANR14>3.0.CO;2-A
- Issue published online: 2 APR 2001
- Article first published online: 2 APR 2001
- Manuscript Accepted: 11 NOV 1999
- Manuscript Received: 21 JUL 1999
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.
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.