The Achilles tendon, named after the seemingly indestructible mythologic Greek warrior, is the largest and strongest tendon in the human body. Achilles tendinitis was the term originally used to describe the spectrum of tendon injuries ranging from inflammation to tendon rupture. Despite this spectrum, through extensive study of the histopathology of Achilles tendinitis, it has been determined that there is no evidence to support primary prostaglandin-mediated inflammation. There are, however, signs of "neurogenic inflammation with presence of neuropeptides like substance P and calcitonin gene related peptide."
Tendon histopathology has been divided into 4 categories1,2,3,4 : (1) Cellular activation and increase in cell numbers, (2) increase in ground substance, (3) collagen disarray, and (4) neovascularization. Using this as a guide, a histopathologically determined nomenclature has evolved to classify this range of Achilles tendon pathology into 3 stages: (1) paratenonitis, (2), tendinosis, and (3) paratenonitis with tendinosis.
Authors Laura M Gottschlich, DO, Kevin J Eerkes, MD, David Y Lin, MD, Evan Schwartz, MD Updated: Dec 15, 2009