The Nail Missed His Foot. Why Was He in Agony?

A builder jumped down onto a plank and a long nail went straight through his boot. He was in such pain that he had to be sedated before anyone could take the boot off.

When they did, the nail had passed between two toes. It had not touched him. There was not a scratch.

His pain had been real the whole time. To see why, you need to know what pain is.

There are no pain nerves

Nothing in your body carries pain. What you have are danger sensors. They report that something is too hot, too sharp or pressing too hard.

A few people are born without working ones. It is not a gift. They injure themselves badly without noticing.

The gate in the spinal cord

The danger signal reaches the spinal cord, which is not a simple relay. It is a gate, and the brain can turn the incoming volume up or down.

That is why rubbing a knock works. Touch signals reach the gate faster and partly crowd out the danger signal. A parent rubbing a bumped knee is using a real mechanism.

The brain answers one question

What reaches the brain is a report. The brain reads it alongside everything else it knows: where you are, what happened last time, whether you are safe.

Then it answers one question. How much does this need protecting?

Pain is that answer. It explains why the same injury can hurt very differently.

• Soldiers with severe wounds often report little pain at the time. Later, in hospital, it hurts as much as you would expect.
• Athletes finish the match and find the break afterwards.
• Severe pain with nothing on a scan is not a contradiction. A scan photographs tissue. It cannot photograph a decision.

Back to the nail

The builder's brain had a nail, a boot, a fall and a plank. Every piece of evidence pointed to a foot with a nail through it. It answered the protection question in the only sensible way.

He was not fooled. Waiting for real damage before producing pain would be a bad design. Pain has to be a prediction, which means it will sometimes be wrong. Being wrong early is the safer failure.

Pain without a body part

Most people who lose a limb go on feeling it. It has a position. It can feel clenched or twisted, and it can hurt for years.

The brain's map of the body outlives the part it was mapping. The region that gets no input does not go quiet. It gets noisy, and neighbouring regions spread into it.

The treatment that often helps is a mirror. The person watches a reflection of the intact limb moving freely, and the phantom often unclenches. The brain was given better evidence and revised its answer.

When pain outlasts the injury

Lasting pain is often treated as proof that damage has not healed. Often the tissue healed and the alarm did not switch off.

A circuit that fires often gets better at firing. The threshold drops. A light touch, a draught or a bed sheet can start to hurt. This is called sensitisation, and it can be measured.

The pain is real. Nothing is wrong with the tissue. Something is wrong with the alarm, and you do not fix a faulty smoke alarm by searching the house for a fire again.

The treatments that help aim at the alarm: graded movement, sleep, and explaining the mechanism. Understanding it measurably reduces the pain.

The placebo is chemical

A sugar pill can produce real, measured pain relief. The brain releases its own opioids. If you give a drug that blocks opioids, the placebo effect disappears. You cannot block something that was never happening.

So expectation is an input to pain. The words said while a treatment is given are part of the treatment.

The short answer

Pain is produced, not received. That does not make it less real. If your pain has outlasted its cause, that is a known problem with a known mechanism. It is worth talking to a clinician who will explain it, and not only scan you again.