Table 1.

Histologic zones of entheses and components of each zone

	Cells	Collagen fibers	Collagen type
Zone 1	Fibroblasts and spindle shaped cells	Linear and parallel	Mainly types I and XII, less type III
Zone 2	Fibrochondrocytes	The linear pattern is lost to an extent, curvy pattern appears	Mainly types I and III
Zone 3	Fibrochondrocytes	Stark irregularity which supports the entheses mechanically	Mainly type II and less type I and X
Zone 4	Osteocytes, osteoblasts, osteoclasts	Site of attachment to bone	Type I only