An excellent TED talk explaining chronic pain

This TED talk does an excellent job of explaining chronic pain.
It includes a case study with a happy ending: CRPS..allodynia...horrid, unrelenting pain, that was resolved.

https://www.youtube.com/watch?v=CZ0gIiwjk_0

Why taking morphine, oxycodone can sometimes make pain worse

This is the best article I have seen on the subject of opioids and hyperalegesia.
The fact is that the phenomena of pain is still poorly understood.

>Ten days after that injury, half the rats received a 5-day treatment of morphine. Then over about 3 months, the researchers periodically measured the rodents’ threshold of pain by poking their hind paws with stiff nylon hairs of varying thicknesses. (The finer the hair that causes the rat to withdraw its paw, the logic goes, the more sensitive it is to pain.) After 6 weeks, injured rats that had received no morphine withdrew from the same kind of pokes as uninjured control rats. But morphine-treated rats remained sensitive to pokes with much finer hairs. It took them 12 weeks to return to the same pain sensitivity as the control rats, the team reports today in the Proceedings of the National Academy of Sciences. Even after the physical injury had presumably healed, they were in pain.<

http://www.sciencemag.org/news/2016/05/why-taking-morphine-oxycodone-can-sometimes-make-pain-worse