I believe it is biochemical. Stress increases cortisol which increases PGE2 cytokines, (cox-2)... these are inflammatory.
It is pretty complex biochemistry... But Dr. Sears has explanations about inflammation in his books.
This is one paper on PubMed:
http://www.ncbi.nlm.nih.gov/pubmed/24553014
http://www.amazon.com/Anti-Inflammat...lammation+zone
Then, mechanisms of inflammatory pain:
http://bja.oxfordjournals.org/content/87/1/3.full
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All truths are easy to understand once they are discovered; the point is to discover them.-- Galileo Galilei
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Weezie looking at petunias 8.25.2017
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