http://medicalxpress.com/news/2016-05-ce...ronic.html -- "'However, it is unclear why these nerves should remain in this overactive, highly sensitive state, even when the initial injury or disease has gone: the back pain from two years ago that never quite went away or the joints that are still painful despite your rheumatoid arthritis being in remission.'"
The reason I always thought the chronic pain (high sensitivity) persists is because it takes a long time for the healed area to toughen up and reach a final state of being healed. It is very hard to say that at any one moment in time the injured spot on the body goes from healing to completely healed. It is gradual process, and because of that, the threshold of pain is lowered by the body on the spot in question to dissuade the person from reinjuring the delicate spot.
The reason I always thought the chronic pain (high sensitivity) persists is because it takes a long time for the healed area to toughen up and reach a final state of being healed. It is very hard to say that at any one moment in time the injured spot on the body goes from healing to completely healed. It is gradual process, and because of that, the threshold of pain is lowered by the body on the spot in question to dissuade the person from reinjuring the delicate spot.