Central sensitization · Chronic pain
The injury is in the tissue. The volume control is in the spinal cord, and an injury can move it.
Central sensitization is a documented change in how the nervous system processes input: the same peripheral signal produces a larger response. It explains pain that outlasts the healing, spreads beyond the injury, and is provoked by things that should not hurt — and it is the mechanism the responding party usually characterizes as psychological.
What it is
Woolf described central sensitization as an amplification of neural signaling within the central nervous system that elicits pain hypersensitivity — a change in the responsiveness of the system rather than a change in the stimulus reaching it.
Once it is present, three things follow that look suspicious to anyone who does not know the mechanism: pain persisting after tissue healing, pain spreading beyond the original territory, and ordinary touch or movement becoming painful.
The IASP definition revision in 2020 made the corresponding point at the level of definition: pain cannot be inferred solely from activity in sensory neurons, and it is always a personal experience shaped by biological, psychological and social factors.
Why it matters in a case
IT EXPLAINS THE THREE THINGS THAT GET CALLED RED FLAGS
Symptoms out of proportion to imaging, symptoms outlasting the expected healing window, and symptoms spreading. All three are predicted by the mechanism. None of them requires a psychological explanation, though the responding party will offer one.
It is also measurable, which is the part that matters most here. Sensory thresholds shift in documentable ways — see quantitative sensory testing.
The limits
Central sensitization is a mechanism, not a diagnosis of exclusion, and it should never be used as a label for pain nobody has bothered to investigate. It coexists with peripheral generators far more often than it replaces them, which is why the structural workup still happens: a sensitized system with an untreated facet joint driving it is still a facet problem.
It also does not establish causation. It describes the present state of the system, not what put it there.
This practice is not aligned to a side. Its obligation runs to the patient’s health and safety, which is the same reason it is not beholden to any position that would keep it from seeing what is actually there. We do not offer opinions on liability, we do not accept a referral or a review conditioned on reaching a particular conclusion, and we will say plainly when the evidence does not support the claim — whichever party was hoping otherwise.
Common questions
Is central sensitization a psychological diagnosis?
No. It is a change in nervous-system signaling. Psychological factors influence pain, as the IASP definition states, but sensitization is not a psychiatric finding.
Can it be measured?
Sensory thresholds can, against published reference values — see quantitative sensory testing. There is no single confirmatory test.
Does it mean the pain is permanent?
No. It can improve, particularly when a peripheral driver is identified and treated and the metabolic terrain is addressed.
Can an injury cause it?
A sustained nociceptive input can drive it, which is the ordinary sequence after a significant injury that is not resolved promptly.
Related reading
- What terrain means
- Quantitative sensory testing
- Why two patients differ
- CRPS / RSD
- The chronic pain epidemic
Ask whether this is the picture in the patient
It changes what is worth testing and what the prognosis honestly is.
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Sources
- Woolf CJ. Central sensitization: implications for the diagnosis and treatment of pain. Pain, 2011. PubMed 20961685
- Raja SN et al. The revised International Association for the Study of Pain definition of pain: concepts, challenges, and compromises. Pain, 2020. PubMed 32694387
- Rolke R et al. Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values. Pain, 2006. PubMed 16697110
- Harden RN et al. Validation of proposed diagnostic criteria (the “Budapest Criteria”) for complex regional pain syndrome. Pain, 2010. PubMed 20493633