Pain can carry on when imaging studies look normal because pain is produced by a protective system and is not read off the tissues like a measurement. Research currently suggests this system can stay active without ongoing tissue damage, so a clear scan does not mean the pain is imagined, and it does not mean nothing can be done.
There is a conversation I have in my rooms most weeks, and it usually starts with an imaging report. The person in front of me has had pain for months, sometimes years, and they have been sent for imaging, and the imaging has come back looking pretty normal for their age. They have been told there is nothing wrong. They have often been told it more than once, by more than one person, and by the time they get to me they are not really asking me to explain the report anymore. They are asking me whether I believe them.
I do, and there is a reasonable scientific account of why the pain can be real and the scan can be clear at the same time. I think the way this gets explained is often what does the damage so let's take it back a notch and work through it slowly.
Pain has never been a damage meter
The common-sense picture most of us grow up with is that pain measures injury, so more damage means more pain and no damage means no pain. That picture works reasonably well for a rolled ankle but it breaks down almost immediately outside of that space. Soldiers have walked away from serious wounds without much pain at the time and people have severe pain in a limb that is no longer there. On the other side, a great many people walk around with disc bulges and rotator cuff changes and knee arthritis on their scans while feeling nothing at all, which is one of the reasons imaging findings need to be interpreted carefully and not read as a verdict of what is causing pain.
So pain is not a readout of tissue state. It seems closer to an output produced by a protective system, and outputs can change when the system changes, even when the tissue does not.
The gap the scans leave behind
For a long time pain medicine described pain in two ways. There is pain that comes from trouble in the tissues, which is what you feel with a sprain or a fracture or an inflamed joint, and there is pain that comes from damage or disease in the nerves themselves, such as the burning, shooting pain of a nerve root problem or of certain kinds of neuropathy.
That leaves a large group of people out. If your tissues look fine and your nerves are intact, and yet you have widespread pain, or a back that has hurt for two years, or a gut that hurts without disease being found, then neither description fits you. For years the label those patients received was idiopathic, or unexplained, which are polite ways of saying we have not got a word for this.
In 2016 a group of pain researchers proposed a third descriptor for that gap, and in 2017 the International Association for the Study of Pain accepted it. The word is nociplastic, and it was defined as pain that appears to arise from altered nociception without clear evidence of tissue damage or of a nerve lesion.
The point of the word was legitimacy. It gave clinicians a way of saying that this presentation is recognised, that it is not a diagnostic failure, and that it is not a polite code for psychological.
The argument that has followed
A paper published in The Journal of Pain in December 2023 by Milton Cohen, John Quintner and Asaf Weisman looks at how that word has been received, and it is unusually honest about the mess.
On one side the term has been embraced so enthusiastically that it has been treated as a synonym for central sensitisation, which is a neurophysiological process, and as a synonym for the coding category chronic primary pain, which is an administrative label. The authors argue that these are three different things in three different domains and that running them together creates confusion instead of clarity. They also point out that nociplastic pain is not a diagnosis, and that as things currently stand there are no validated clinical criteria for identifying it.
On the other side, some senior figures have rejected the term outright, on the grounds that you cannot have altered nociception if the nociceptors were never switched on in the first place.
Where their answer comes from
Their answer is a piece of history, and I found it the most interesting part of the paper.
Sir Charles Sherrington, who did the foundational work on this in the early 1900s, described the skin as having, in his words, "a special sense of its own injuries". He coined the word nociceptor, meaning harm detector. What is easy to forget is that his idea of nociception covered the whole protective process and not only the detection. He wrote that it
"is essentially the whole of the process which deals with both the reception of nervous impulses of a noxious type and the responses intended to prevent or mitigate harm"
Sir Charles Sherrington, on nociception
In 2008, when the formal definitions were codified, that description was narrowed to the input side only, so nociception became the neural process of encoding noxious stimuli and nothing more. The response half fell out of the definition.
Cohen and his colleagues propose bringing the broader idea back, under the name of a nociceptive apparatus, and they suggest that activation of that apparatus is necessary but not sufficient for pain. In plain terms, something in the protective apparatus has to be active for you to hurt, and that activity on its own does not guarantee that you will hurt.
The reason this matters for the person with the clear scan is what follows from it. If the protective apparatus is distributed through the spinal cord and the brain, and if it sits in close conversation with the immune system and with the body's stress circuitry, then it may be possible for it to become more active without the signal starting in the tissues at all. The authors are careful to present this as a proposal that still needs testing, and I am going to be equally careful, because it is a hypothesis and not a finding.
What I think this means in the room
It means that a normal scan and real pain are not a contradiction, and you do not have to choose between believing your body and believing the report.
It means that nobody should be handing you nociplastic pain as a diagnosis, because it is not one. It is a description of a pattern, one that fits a recognised group whose mechanisms are still being worked out.
It also means that treatment tends to be aimed at the whole protective apparatus and not at a spot on a scan, and that is where graded exposure, education, sleep, stress and a gradual return to movement come into it. I am not going to promise you that any of that resolves persistent pain, because the evidence does not support that promise for everyone, and this paper says nothing at all about treatment. What the research currently suggests is that approaches which work with the protective system tend to do better over time than repeatedly investigating tissue that has already been cleared.
If you have been carrying pain that nobody has been able to explain, what I would want to do is take a proper history, examine you carefully, look at what has already been done and where the gaps are, and then have an honest conversation about what is likely to help and what is not. If something in that assessment suggests we are dealing with something that sits outside what I do, then the most useful thing I can do is recognise that and get you to the right person. Either way, you should leave with an explanation you can repeat to your family, and with a sense that you were listened to.
Common questions
Does a clear scan mean the pain is not real?
No, and the reason is that imaging tells us about tissue while pain is produced by a protective system, so the two can disagree without either one being wrong. A normal imaging report is useful for what it rules out, and it doesn't tell us anything about whether you are sore.
What is nociplastic pain?
It is a descriptor the International Association for the Study of Pain accepted in 2017 for pain that appears to arise from altered nociception without clear evidence of tissue damage or of a nerve lesion. It is not a diagnosis, and there are currently no validated clinical criteria for identifying it, so it describes a pattern and not a cause.
Should I have more imaging if the pain has not settled?
That tends to depend on what has changed since the last set. If nothing new has appeared and the previous imaging was reasonable for your presentation, repeating it often adds little, and where there are new signs or a change in pattern it can be worth revisiting. That's a conversation to have with the doctor who would be ordering it.
What can be done when the imaging is clear?
Treatment in that situation tends to be aimed at the protective system as a whole and not at a spot on an imaging report, so it usually involves a proper assessment, an explanation you can repeat, graded exposure, sleep, stress and a gradual return to movement. I can't promise that resolves persistent pain for everyone, and the research currently suggests those approaches do better over time than repeated investigation of tissue that has already been cleared.
