Chronic pain and the nervous system: why pain stays after the wound has healed

“My ankle healed two years ago. The X-ray looks fine and the orthopaedic surgeon is happy. And yet, when I step off the kerb, it stabs as if it happened yesterday.”

People who say this usually aren’t expecting an answer. They’re expecting doubt. Because they’ve heard it from others already: that it should have passed by now, that a little patience is needed, that perhaps they pay too much attention to it. And they ask themselves the same. If the tissue is healthy, where does the pain come from? Are they imagining it? Are they weak? Did the doctor miss something?

This post is an attempt to answer that question — not with comfort, but with an explanation of how the nervous system creates pain and why it can keep it going long after the reason for it has gone. What I am going to write does not mean the pain is “all in your head”. It means something more interesting: pain is always also in the head, even when the ankle is still broken.

When pain outlasts the wound

We speak of chronic pain when pain lasts or keeps returning for more than three months. The threshold isn’t arbitrary: most tissues heal within that time, so pain that lasts longer often no longer follows the injury but lives a kind of life of its own.

It isn’t rare. In a large European study in which Breivik and colleagues surveyed adults in fifteen European countries and Israel in 2006, 19 per cent of respondents reported moderate or severe chronic pain — roughly one adult in five. Many of them said the pain affected their work, sleep and relationships, and a large proportion felt their pain was not being adequately managed.

The International Classification of Diseases, ICD-11, made an important shift here. For the first time it introduced a category of chronic primary pain — pain that is not merely a symptom of some other disease but a condition in its own right. It includes, for example, some forms of low back pain, fibromyalgia and also irritable bowel syndrome. With this, the profession officially recognised something people with chronic pain have known for a long time: pain can become independent.

Pain is an alarm, not a damage meter

At school we learned a simple picture: something in the tissue is damaged, a nerve reports it to the brain, the brain registers pain. Like a doorbell that rings when someone presses the button. That picture isn’t entirely wrong, but it is incomplete — and what’s missing is exactly where the explanation of chronic pain lies.

As early as 1965, Ronald Melzack and Patrick Wall proposed the “gate” theory: a signal from the body doesn’t travel to the brain unchanged, but is amplified or dampened in the spinal cord. Today we know even more. The brain doesn’t simply receive the signal from the body; it evaluates it: is this dangerous? In doing so it takes into account past experience, current mood, context, expectations, sleep and stress. Pain is the conclusion of that evaluation — a warning that the body needs protecting.

In 2020 the International Association for the Study of Pain wrote this into its official definition too: pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. And it added an important note — pain and nociception (the detection of a harmful stimulus) are not the same thing. You can have pain without injury and injury without pain.

With acute pain this system is extremely useful. Thanks to it you don’t stand on a broken leg and you don’t touch a hot hob twice. With chronic pain, however, the alarm can stay on even when there is no longer a fire — or go off at the first wisp of smoke from the kitchen.

When the amplifier is turned up

One of the mechanisms that explains this is called central sensitisation. Clifford Woolf, who researched the phenomenon for decades, describes it as a state in which the responsiveness of the neurons that carry pain increases within the nervous system. The system learns: the more it has been on standby, the more easily it goes off.

In practice this means several things that people with chronic pain know well:

• The pain spreads. It started in the lower back; now the buttock, the thigh and the shoulders hurt too.
• Touch that shouldn’t hurt, hurts. A waistband, a hug, light pressure.
• The pain is out of proportion. A small movement sets off a reaction as if something serious had happened.
• It varies from day to day. After a bad night, an argument or a tense week the pain is worse, even though nothing new has happened to the tissue.

It is important to understand that this is a physiological change. It isn’t imagination and it isn’t a character trait. It is learning — and the nervous system learns pain too. The good news that follows is that what has been learned can, to some extent, be unlearned.

An interesting insight into how pain gets “written in” came from research by Apkarian’s group. In 2012 Baliki and colleagues followed people with new-onset low back pain and found that the strength of connections between brain areas involved in emotional evaluation and learning predicted who would go on to develop chronic pain. In other words, the transition to chronic pain didn’t depend only on what had happened to the back, but also on how the brain responded to it.

Because pain, fear and emotion are so intertwined, I have written a short explanation of pain and emotion in the knowledge base. On the wider picture of why the body carries what is going on inside us, I wrote in the post “The tests are normal, but it still hurts”.

The cycle of fear and avoidance

With chronic pain one more thing almost always happens: the person starts to interpret the pain, and that interpretation becomes part of the pain.

In 2000 Johan Vlaeyen and Steven Linton described a model that is today one of the most widely used in understanding chronic pain — the fear-avoidance model. It starts with pain. If a person understands it as a sign that something in the body is tearing and wearing out — if they catastrophise — a fear of movement appears. Fear leads to avoidance: less walking, less bending, more resting, guarding the painful spot. In the short term this is logical. In the long term, though, the body loses strength and mobility, tension rises, mood drops, and the alarm becomes even more sensitive.

The model isn’t an accusation. Nobody avoids movement out of laziness; they avoid it because they are afraid, and with pain fear is an understandable response. The only problem is that avoidance helps you today and harms you tomorrow — just as with anxiety. Anyone who knows health anxiety will recognise a familiar pattern in this cycle: constantly checking the body, seeking new opinions, and attention that keeps returning to the painful spot.

Pain doesn’t live alone: what happens at home

As a marriage and family therapist in training, I also look at pain through relationships. Chronic pain never affects just one person. It changes who cooks, who carries the shopping, who goes on the outing and who stays at home. It changes sex, holiday plans, conversations over dinner.

Research that has followed couples shows that a partner’s response is an important part of the story. Back in the 1990s, Romano and colleagues observed couples in which one partner lived with chronic pain and found that overly solicitous responses from the partner — “leave it, I’ll do it”, “don’t you bend down” — were linked to greater disability in the person who was in pain. That doesn’t mean care is wrong. It means that loving care which takes over everything can unintentionally confirm the message: “Your body is fragile. Don’t trust it.”

Often the opposite happens too. The partner grows tired, starts to doubt, quietly thinks it should have passed by now. The person in pain senses this and has to fight for their pain over and over again. The feeling that nobody believes you is one of the most powerful amplifiers of pain I know.

A conversation might sound like this (composed, not a real person):

“You’ve been lying down all day again.”
“Because it hurt.”
“I know. It’s just … sometimes I think you’re afraid to get up.”
“You mean I’m exaggerating.”
“No. I mean I miss you.”

There are two truths in this short exchange, and both hold. She really does feel pain. He really does notice the fear. When a couple learns to talk about both at once — without proving who is right — some of the tension that keeps the pain going often loosens too. In relational family therapy, in which I am training, this is exactly what interests us: how one person’s distress flows through a relationship, and how the relationship can become a place where the body settles.

A doctor first — and why that isn’t a formality

Before I go on, something I want to state very clearly. An explanation about the nervous system does not replace a medical examination. Chronic pain may have a cause that needs treating — an inflammatory disease, nerve damage, the consequence of an injury that wasn’t recognised, or something else entirely. Physical causes need to be ruled out first, and that isn’t a formality but a precondition.

See a doctor as soon as possible, especially if the pain comes with any of the following:

• unexplained weight loss, fever or night sweats,
• pain that doesn’t ease at night and doesn’t change with movement or position,
• tingling, numbness or weakness in the arms or legs,
• problems passing urine or controlling your bowels,
• pain after a fall or accident, or if you have ever had cancer.

But I want to say this just as clearly: even when a cause is found — or ruled out — the pain is not “all in your head”. Never. The nervous system is part of the body. Pain that the nervous system amplifies or sustains is just as real as pain from a fracture. The only difference is where to look for the paths that help.

What helps: from explanation to relearning

With chronic pain, the approach that has proved most effective combines several professions: a doctor, a physiotherapist and psychological treatment. Not because the pain is “half physical and half psychological”, but because the nervous system connects both.

Explanation helps in itself. People who understand how pain is created are often less afraid of it, and less fear means less amplification. Physiotherapists call this pain neuroscience education.

Gradual movement. Not “grit your teeth and push through”, but agreed small steps through which the body gains new, safe experiences. That way the nervous system gets evidence that movement isn’t dangerous.

Psychological treatments. Cognitive behavioural therapy and acceptance and commitment therapy have good research support for chronic pain. They don’t promise the pain will disappear, but that its impact on your life will lessen — and for many people the pain itself lessens too.

Pain reprocessing. A newer approach called pain reprocessing therapy builds directly on the idea that the nervous system can “unlearn” the alarm. In 2022 Ashar and colleagues tested it in people with chronic back pain: after treatment, most participants in that group reported being pain-free or nearly pain-free, considerably more than in the comparison groups. The study was encouraging, but it was a single study and involved relatively mild to moderate pain — I write about its limits below.

Sleep and stress. Because poor sleep amplifies pain and pain spoils sleep, the loop between them deserves special attention. I wrote about how a sleepless night changes how we experience everything in Sleep and emotion: why everything hurts more after a bad night. When pain is tangled up with low mood, have a look at Depression and the body: pain, fatigue and digestion too.

In Slovenia these treatments are offered by pain clinics and rehabilitation programmes, to which your doctor can refer you. Psychotherapy can be one part of that picture — never the only one.

Exercise: observing pain without the alarm

This exercise comes from what is known as somatic tracking, used in pain reprocessing approaches. The point isn’t to drive the pain away, but to look at it from a different angle. You can do it today, when the pain isn’t at its peak. It takes five minutes.

1. Get comfortable and for a few breaths simply watch your breathing. Let the out-breath be a little longer than the in-breath.
2. Turn your attention to the pain as if you were observing it for the first time. Where exactly is it? What shape is it? Is it dull, sharp, throbbing, burning? Does it move or stay still?
3. Notice the thoughts that come along with it — “here it is again”, “it’s going to get worse” — and name them: “this is a thought”. Don’t argue with them; just notice them.
4. Repeat a calm message of safety to yourself, one your doctor has also confirmed: “My nervous system is creating these sensations. My body is safe.” Notice whether anything changes — intensity, shape, location.
5. Finish with one thing you will do today despite the pain, however small: a short walk, a call to a friend, a coffee on the balcony.

If the pain rises during the exercise, nothing is wrong. Stop, move a little and try another time. The exercise isn’t a test. It is a way of offering your nervous system an experience other than alarm.

Where this explanation falls short

I want to be honest about the limits of what I have written, too.

Not all chronic pain is mainly a matter of the nervous system. With rheumatoid arthritis, cancer, diabetic neuropathy or after nerve injury there is a clear physical process in the background that needs treating. The nervous system still plays a part in how much it hurts, but the “alarm” explanation isn’t an adequate answer there.

Psychological treatments aren’t miracles. For many people they reduce pain and improve life; for some only a little. The pain reprocessing study was encouraging, but it needs to be repeated, in larger groups and with more severe forms of pain. Anyone who promises that one method will make pain disappear for everyone is promising too much.

The explanation can be turned against the person. If someone hears “your brain is creating the pain” as “it’s your own fault”, the explanation harms them. The nervous system learned pain in circumstances nobody chose — after an injury, during a period of severe stress, after trauma that became written into the body. Responsibility for what happened isn’t yours. What is yours is the possibility of trying to change something — and even in that you deserve help.

And we mustn’t forget: sometimes pain is bound up with a life that can’t simply be changed. Unbearable conditions at work, caring for an ill relative, violence at home. If you are living with violence, call the SOS helpline for women and children victims of violence on 080 11 55 in Slovenia, and in an emergency 112 or the police on 113. If pain brings you to the thought that you can’t go on, call the Samaritan helpline (Zaupni telefon Samarijan) on 116 123 in Slovenia (24 hours) or the mental distress helpline (Klic v duševni stiski) on 01 520 99 00 in Slovenia (from 7 pm to 7 am).

If pain has stopped you in the middle of an active life, the post Injury and mental health: when your body stops you may also speak to you. And because similar mechanisms show up in the gut, have a look at Irritable bowel syndrome and stress: the axis between the gut and the brain as well.

What to remember

• Pain is an alarm, not a damage meter. The brain assembles it from bodily signals, experience, fear and circumstances.
• With chronic pain the nervous system can tune itself to greater sensitivity — a real physiological change, not imagination.
• A doctor first. Physical causes need to be ruled out or treated; but pain is never “all in your head”.
• Fear, avoidance, poor sleep and the feeling that nobody believes you amplify pain; understanding, gradual movement and safe relationships can quieten it.
• Pain lives in relationships too — and a relationship can be part of the way out.