@RingoStar CS isn't a new problem but it's fairly new to the medical community. If you ask docs about it, most will recognize the term and shrug it off. That's impart because it's very poorly understood in general. Everything involving the brain is poorly understood. Essentially what happens, you have a painful stimulus and your CNS (brain/spinal cord) does what they call "wind up." Your body doesn't like pain and your CNS is designed to minimize it. This is the classic "fight or flight" response of the sympathetic nervous system. See a bear, run away. When pain is severe and seems to last along time, your CNS gets stuck in the chronic state of fight or flight. Doing so takes a major toll on your body as do the antagonist systems.
That's about all they truly understand. Some believe that your body gets hard coded, like you said, and you feel the pain even long after the injury has healed. This is where allodynia vs hyperalgesia comes into play. Others argue that the injury never truly heals and you develop this hyper state of pain. This is often the case with peripheral nerve injury. You get this neuroinflammatory condition that can move around the body. They believe this is how RSD/CRPS, even fibromyalgia begin to develop.
There are a couple important take always here. Your sympathetic and parasympathetic (feed and breed) nervous systems prefer balance. If one goes on overdrive, it's typically at the expense of the other. This is why things like sleep, sex, and digestion are affected. You hear complaints of impotence, IBS, and fatigue. Your body is burned out from sympathetic overdrive. All the systems that were trying to help "that caveman run away from that bear" get stuck in the "on" position. The last thing your brain wants to do is have sex and eat a sandwich when you're running from that bear.
This is also why patients can go on to develop completely unrelated issues. I've developed bad arthritis, fatigue, apnea, chronic migraine, intracranial hypertension, and of course depression and anxiety.
Treatment is as difficult as understanding to issue. Are we chronically hurt, are we healed but the brain can't shut it off? Who the hell knows. The only thing I understand is how closely I can relate.