Chron. Achillodynie

Chronic Achillodynia:

The tendon is usually thickened in the chronic stage. The chronic inflammation causes lasting pain (often a deep dull pain) and leads to a weakening of the Achilles tendon. The cause of this lies in the fact that the Type 1 collagen that makes up 95% of collagen in a healthy Achilles tendon has been replaced by the significantly weaker Type 3 collagen. This also happens in the context of Achilles tendon injuries, as the fibroblasts that migrate from the blood vessels as a reaction to the injury primarily produce Type 3 collagen. The Achilles tendon can sometimes later tear as a result.

New research shows that an additional problem is that growing blood vessels, which should heal the Achilles tendon, also pick up small nerve endings, which can react to pulling with severe pain.