Enthesis

Enthesis (plural: entheses) is the point at which a tendon or ligament^[1] or muscle^[2] inserts into bone, where the collagen fibers are mineralized and integrated into bone tissue. These insertion points are commonly called Sharpey's fibers.

Classification

There are two types:

• Fibrous entheses
• Fibrocartilaginous entheses

In a fibrous enthesis, the collagenous tendon or ligament directly attaches to the bone, whilst the fibrocartilaginous enthesis displays 4 zones during the transition from tendon/ligament to bone:

• i) tendinous area displaying longitudinally oriented fibroblasts and a parallel arrangement of collagen fibres
• ii) a fibrocartilaginous region of variable thickness where the structure of the cells changes to chondrocytes
• iii) an abrupt transition from cartilaginous to calcified fibrocartilage - the so-called 'tidemark' or 'blue line'
• iv) bone

Pathology

A disease of the entheses is known as an "enthesopathy" or "enthesitis" and is characteristic of spondyloarthropathy but is present in other pathologies as well.

References

External links

• Image of enthesis at Medscape
• Enthesopathy and Soft Tissue Shadows at chiroweb.com
• Resnick D, Niwayama G (1983). "Entheses and enthesopathy. Anatomical, pathological, and radiological correlation". Radiology 146 (1): 1–9. PMID 6849029. http://radiology.rsnajnls.org/cgi/content/abstract/146/1/1. 
• Origin of phrase at rheuma21st.com at rheuma21st.com

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