His pain was completely real. It just wasn't coming from his foot.
That case, reported in the British Medical Journal, is the doorway into the most useful idea in modern pain science: pain is not a measurement of damage. It is your brain's best guess about how much danger you're in, and how much you need to protect yourself.
The alarm and the decision
Your body is wired with sensors called nociceptors. They respond to things that could harm tissue: heat, pressure, chemicals released by injury. When they fire, they send signals up the spinal cord. That process has a name, nociception, and it is not the same thing as pain.
Pain is what happens next. Your brain takes the danger signal and weighs it against everything else it knows. Where are you? What happened last time? Is there a lion chasing you? Do you believe this is serious? Then it produces an output: pain, a little or a lot, or sometimes none at all.
Nociception is the alarm going off. Pain is the brain deciding how loud to make the siren.
The world's main pain research body, the International Association for the Study of Pain (IASP), rewrote its official definition in 2020 to reflect this. Pain is now "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage." The notes that come with it say plainly that pain and nociception are different things, and that pain can't be inferred from activity in sensory nerves alone.
The evidence that the brain is in charge
Once you see it, examples are everywhere.
Damage without pain. During the Second World War the American anaesthetist Henry Beecher questioned 215 seriously wounded soldiers on the Italian front. By his account, about three-quarters had little enough pain that they didn't ask for relief. Beecher's explanation was meaning: for a soldier, a wound could be a ticket home. Years later he found that civilians with comparable surgical wounds asked for pain relief far more often. Same tissue damage, different meaning, different pain.
Pain without damage. The builder's foot. Or phantom limb pain, felt in an arm or leg that is no longer there. A 2020 review of 39 studies estimated that about 64% of people with amputations experience it. There is no knee left to hurt, and the knee still hurts.
Damage that doesn't predict pain. Backs are the clearest case. A 2015 review pooled MRI scans of more than 3,000 people who had no back pain at all. Disc degeneration showed up in 37% of 20-year-olds and 96% of 80-year-olds. Disc bulges appeared in 30% of 20-year-olds and 84% of 80-year-olds. Many of the "findings" on a scan are as normal as grey hair.
| What you might hear | What it often means |
|---|---|
| "Degenerated disc" | Normal ageing, common in people with no pain |
| "Disc bulge" | Seen in about a third of pain-free 20-year-olds |
| "Wear and tear" | A description, not a diagnosis of where your pain comes from |
None of this means scans are useless. Some findings matter a great deal. It means the picture and the pain are only loosely linked.
Why chronic pain is a different animal
Short-term pain is mostly a good alarm: you touch the stove, you pull away. The trouble comes when pain lasts beyond normal healing, usually three months or more. That is common. In 2023, 24.3% of US adults reported chronic pain, according to the National Center for Health Statistics, and 8.5% had pain serious enough to limit daily life most days.
In chronic pain the alarm system itself can become more sensitive. The nervous system learns, and with long practice it gets very good at producing pain. Signals that used to be ignored now get through, and movements that are perfectly safe start to hurt. Fear plays a part. If you believe every twinge means harm, you move less and guard more, and the brain takes that as proof the danger is real.
Hurt and harm are not the same thing, especially when pain has been around a long time.
This is also why treatments that change the brain's interpretation can work. In a 2021 trial in JAMA Psychiatry, people with chronic back pain (most of it moderate rather than severe) were given about four weeks of pain reprocessing therapy, which teaches them to see their pain as a safe but oversensitive brain signal. Afterwards, 66% were pain-free or nearly so, compared with 20% of a group given a placebo injection. It was one trial, it needs repeating, and it doesn't apply to every kind of pain. But it shows that understanding pain can change it.
What this does not mean
It does not mean "it's all in your head" in the dismissive sense. Every pain is produced by the brain, including a broken leg. Calling pain brain-made doesn't make it imaginary. It puts it in the system that actually runs it.
It also doesn't mean you should ignore pain. New, severe, or unexplained pain, especially with swelling, fever, numbness, weakness, or loss of bladder control, needs a doctor.
The levers you actually have
Because the brain weighs context, context is something you can change:
- Learn what's going on. Fear amplifies pain, and so does a frightening diagnosis you don't understand. Ask what a scan finding means in people without pain.
- Move, gradually. For many chronic conditions, careful, graded movement teaches the system that the movement is safe. Start below the level that flares you up and build slowly.
- Sleep, stress, mood. All of them turn the volume up or down. A bad week at work can make a sore back worse without the back changing at all.
- Attention and meaning. Absorbing activities and a sense of safety turn the volume down. Pain gets loudest when you're anxious and focused on it.
The takeaway
Pain is the brain's protective output, not a damage meter. That is why people can have injuries without pain, pain without injuries, and scans that barely match how they feel. When pain becomes chronic, the alarm itself grows oversensitive, and the most effective treatments often work by teaching the brain that it is safer than it thinks.
Try this: next time something hurts, ask two questions: "How much damage is likely here?" and "What else is turning the volume up right now: fear, fatigue, stress?" Separating the two is the first move in every modern pain treatment.
Sources & Further Reading
Sources
- The nail case: a 1995 case report in the BMJ, widely retold in pain-science teaching (for example in Joshua W. Pate's TED-Ed lesson The mysterious science of pain).
- IASP revised definition of pain and accompanying notes: Raja et al., Pain 161(9), 2020.
- Beecher, H.K. "Pain in Men Wounded in Battle." Annals of Surgery 123, 1946; and his 1956 JAMA comparison with civilian surgical patients.
- Phantom limb pain prevalence (64%, 39 studies): Limakatso et al., PLOS ONE, 2020.
- MRI findings in people without back pain: Brinjikji et al., American Journal of Neuroradiology, 2015.
- Chronic pain prevalence (24.3%, high-impact 8.5%): NCHS Data Brief No. 518, 2024 (2023 data).
- Pain reprocessing therapy trial: Ashar et al., JAMA Psychiatry, 2022 (published online 2021).
Go deeper
- 📘 Explain Pain — David Butler & Lorimer Moseley (the classic plain-language guide)
- ▶️ "Why Things Hurt" — Lorimer Moseley, TEDxAdelaide (a funny, unforgettable 15 minutes, including the snake bite he mistook for a scratch)
- 📘 The Way Out — Alan Gordon (the pain reprocessing approach, by its developer)
- 🌐 Pain in the US, 2023 — CDC/NCHS data brief
Sensitive-topic note: this piece is general information, not medical advice. Pain that is new, severe, getting worse, or comes with fever, numbness, weakness, or loss of bladder or bowel control needs prompt medical attention. Chronic pain is real and treatable; a doctor or physiotherapist who understands modern pain science is worth finding.