Why pain can last after an injury has healed

You hurt your back lifting something awkward. It was agony for a week, bad for a month, and then it was supposed to get better. Months later, it hasn’t. The scan shows nothing that explains it. The physio says the tissue has healed. Someone, meaning well, tells you there’s nothing wrong.

And what you hear is: it’s in your head.

It isn’t. Or rather, it is, and so is every pain anyone has ever felt. That isn’t the same as imagined, and understanding the difference is one of the most useful things a person living with pain can learn.

What pain actually is

We tend to think of pain as a measurement. Damage happens in the body, a signal travels up to the brain, and the brain reports how bad the damage is. More damage, more pain.

It doesn’t work like that. Pain is something the brain produces, not something it receives. It weighs up everything it knows: the signals coming in from the body, but also what happened last time, what you’re afraid of, how much sleep you’ve had, how safe you feel right now. Then it decides how much protection you need. Pain is that decision. It’s an alarm, and its job is to make you stop, guard, and pay attention.

This isn’t a fringe idea. In 2020 the International Association for the Study of Pain revised its official definition of pain for the first time since 1979. It now describes pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Its notes go further: pain and the nerve signals from damaged tissue are different things, pain is always a personal experience shaped by biological, psychological and social factors, and a person’s report of pain should be respected.

That last point matters. Pain without visible damage is still pain.

The builder and the nail

In 1995 the BMJ ran a short item about a 29-year-old builder who came into an emergency department after jumping down onto a 15 cm nail. It had gone straight through his boot. The smallest movement of it was so painful that he had to be sedated with fentanyl and midazolam before it could be pulled out.

When they took his boot off, the nail had passed cleanly between his toes. His foot was uninjured.

It was a photograph and a few lines, not a full case study, and some pain scientists think there was probably more to it than that. But the point it makes is real. His brain saw a nail through his boot, concluded the worst, and gave him the pain of the worst. The pain was real. The damage wasn’t.

The limb that isn’t there

If you want proof that pain doesn’t need tissue, think about phantom limb pain: pain felt in an arm or leg that has been amputated. There is nothing there to be damaged. And yet a review published in 2020, pooling studies of people with amputations, found that around 64 per cent of them experience it.

The pain is in a limb that doesn’t exist, because the brain’s map of that limb is still there.

When the alarm gets turned up

After an injury, it’s normal for the area to become more sensitive for a while. Things that wouldn’t usually hurt, do. That’s protective: it keeps you careful while you heal. Usually, as the tissue mends, the sensitivity settles too.

Sometimes it doesn’t. The nervous system itself becomes more sensitive and stays that way, turning the volume up on signals that wouldn’t have bothered it before. It has, in a sense, learned pain. The alarm is now set to go off earlier and louder, long after the original danger has passed.

And it isn’t only signals from the body that turn the volume up. Fear does. Stress does. Bad sleep does. Rewiring Pain puts it simply: pain grows louder in a body that does not feel safe. A nervous system that feels threatened tightens muscles, sharpens attention and heightens sensation. That isn’t imagined. It’s physiology.

You are a long way from alone

Persistent pain is far more common than most people realise. A review of UK studies published in 2016 estimated that around 43 per cent of adults, roughly 28 million people, live with chronic pain. For somewhere between one in ten and one in seven adults, it is moderately or severely disabling.

If you’ve felt like the only person who can’t explain why they still hurt, you’re not.

Hurt doesn’t always mean harm

Here is the shift that changes things for a lot of people. In acute pain, pain is a fairly reliable sign of damage, and stopping is wise. In persistent pain, that link has loosened. The alarm is sensitive, not accurate. A movement that hurts isn’t necessarily doing harm.

That matters because of what pain teaches us to do. If every bend of your back hurts, the natural thing is to stop bending. You move less, and more carefully. Over time, the muscles weaken and stiffen, the movements you avoid start to feel more dangerous, and the nervous system, with less and less evidence that you’re safe, stays on guard. The protection becomes part of the problem.

The way out is not to push through and ignore it. It’s to give the nervous system new evidence, gently and repeatedly, that movement is safe. A little more than last time, not a lot. Pacing your activity across the day instead of doing everything on a good day and paying for it for three. Treating a flare-up as a setback, not a verdict.

Learning safety

There is good evidence that simply understanding how pain works helps. A review of thirteen trials of pain education for people with long-term musculoskeletal pain found that it reduced pain, improved function, lowered disability and helped people move more.

That’s the hopeful part. A nervous system that has changed can change again. The same ability to learn that turned the volume up can, with time, turn it down. Or, as the book says:

A nervous system that has learned pain can also learn safety.

It is slow, and it isn’t a cure. But it’s real, and it puts some of the control back in your hands.

Before you do anything

Pain that’s new, pain after an injury, or pain that comes with other symptoms needs a proper assessment from your GP or another clinician first. This is about the pain that has been checked, has outlasted its cause, and still won’t let go.

Rewiring Pain is about that pain: how the brain learns it, why it lingers, and how it can learn safety again. Not a promise of a pain-free life. Something more honest than that.

Hope does not mean promising a pain-free life. Hope means restoring choice.