Pain is an output of the brain, not a direct readout of tissue damage. This is one of the most important and least understood facts in modern pain science. Chronic pain, pain lasting more than three months, is almost always driven by a sensitised nervous system rather than by ongoing tissue damage at the site where the pain is felt.
Central Sensitisation: What Is Actually Happening
Central sensitisation is the state in which the central nervous system becomes hyperresponsive to input. Normal sensations are amplified and perceived as painful. The nervous system, designed to protect you, has become over-protective. This is why people with chronic back pain often find that light touch, temperature changes, or movement that should not be painful produces a significant pain response.
The MRI Problem
Studies imaging the spines of pain-free adults consistently find disc bulges, herniations, and degenerative changes in a significant proportion of the population. These findings do not predict pain. Conversely, many people with severe chronic back pain have structurally normal MRI findings. The relationship between tissue damage and pain is far weaker than the medical system has historically suggested. This is not dismissive. It is actually good news, because it means most chronic pain is modifiable.
Most chronic pain is maintained by the nervous system, not by tissue damage. That makes it more treatable, not less.
The Clinical Implication
Treating chronic pain requires addressing the nervous system, not just the tissue. This means appropriate progressive loading, not rest, to reduce the threat value the brain associates with movement. It means addressing sleep, stress, and psychological factors that amplify the pain signal. It means understanding that hurting does not necessarily mean harming.