The Achilles tendon is made up of collagen fibres which are similar to a rope.
Sometimes certain factors overload the Achilles tendon. The body initially responds to overload with inflammation and cells called fibroblasts make new collagen in an attempt to bridge the gap caused by the injury.
Continued walking and other influencing factors causes further stress, which limits the body’s ability to heal. As the condition progresses over weeks to months the inflammation diminishes and the collagen starts to unwind and unravel and then it breaks apart and becomes fragmented.
At the same time the collagen is unwinding and breaking apart, fibroblasts are enlarging in an attempt to make more and more collagen. But, the unravelling outpaces the new collagen formation.
Many new blood vessels are made quickly in an attempt to provide more blood flow to the area, but these vessels are abnormal and immature, and therefore are not very good at their job. The collagen that is created and added to the injured site is done so quickly and in a very disordered manner.
The cell enlargement, poor blood flow, old collagen unravelling and disorganised new collagen all contribute to the degeneration of the Achilles at its insertion.
In some cases of insertional Achilles tendinopathy the degeneration causes the tissue to calcify forming a retrocalcaneal exostosis. It is not know whether the retrocalcaneal exostosis causes the irritation or is a result of the irritation.
