Pain Comes From Conditions, Not Just Tissue

"Some days I put my shoes on without a second thought. Other days I cannot bend at the waist."

I hear this often from people who have been in pain for a long time. And they usually add something like this: "It's not as if anything could have changed in those few days."

They are right. A disc does not herniate or retract overnight. Worn cartilage does not grow back. The shape of the cartilage or the disc is not much different from yesterday. But the degree of pain is.

So what changed in those few days?

Even within the same body, it differs from day to day

Pain is said to differ from person to person. But people who have lived with long-standing pain actually run into something more often: a difference within the same body.

They tell me last week was bearable but this week is unbearable. Some mornings walking is fine, and by evening it has gotten worse.

The shape of the tissue could not have changed back and forth in that time. What changed was not the tissue, but the conditions the tissue was sitting in.

The signal that says "it hurts" does not come from the tissue

The signal that says it hurts does not come from the cartilage. It comes from the nerve endings that reach into it. And nerve endings cannot read the shape of the tissue. They read the state of what is around them.

Among the conditions that trigger a nerve, pressure is a large share. It does not matter whether the pressure comes from outside, pressing in, or from fluid building up and pushing from within. Muscle and blood vessels can stretch or shift aside and protect themselves to some degree, but nerves have a harder time doing that. So as long as the pressure continues, the nerve keeps firing.

And a compressed spot also gets less blood flow. In Korean medicine there is a saying, 불통즉통(不通則痛) — "where there is no free passage, there is pain." This old line meets, in places, what we now describe in terms of circulation.

The chemical state of a spot also becomes a signal. In one study, injecting an acidic solution into the muscle of a healthy person caused pain — even though the stimulus was neither an injury nor an inflammatory trigger.

The conditions are not confined to the painful spot

People often say the whole body hurts more after a poor night's sleep. That is not just a feeling. When healthy people are kept awake for one night and then tested, the threshold at which they begin to feel pain actually drops, and the body's own pain-suppressing power weakens at the same time.

It is not only sleep. Prolonged hunger, exhaustion, cold, and shifts in the concentration of body fluids all make muscles tense on their own. The body protects what it needs to protect first, and passes the burden on somewhere else. Wherever receives that burden is where it hurts.

And this path does not run in only one direction. Pain itself can affect the nervous system and the immune system throughout the body. That is why I do not treat a report of pain as the business of one spot alone.

Shape does not determine pain

I do see people whose curvature is noticeably severe yet who report no discomfort at all. I also see people whose shape looks fairly unremarkable on imaging yet who have been in pain for a long time.

What separates them? Whether the body has finished adapting to that shape plays a part. Nerves are lenient toward familiar stimuli and sensitive to new ones. So even with the same shape, what a person experiences differs depending on whether the body is still adjusting to it or has already finished adjusting.

But how much this varies differs a great deal from person to person. In a study that repeated the same stimulus on pain-free adults, the pain response blunted in 12 percent, actually grew stronger in 29 percent, and stayed unchanged in 59 percent — the largest group. You cannot say that everyone simply gets used to it over time.

This is not to say tissue does not matter

This is not saying "the tissue is fine, the problem is somewhere else."

A tear is a tear, and a fracture is a fracture. What happened to the tissue has to be assessed as such. But the conditions the tissue sits in are always present alongside it, and the longer pain has lasted, the more layers tend to overlap.

This is not a question of choosing between tissue and conditions. It is a matter of seeing which layers are present together, and which one carries the larger share right now.

When to get checked first

If the pain began suddenly without an injury, keeps getting worse even with rest, wakes you at night, comes together with fever or weight change, or comes together with weakness or numbness — there is something to check before this discussion applies. Looking at the conditions of that spot comes after that.

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Let us go back to the shoes.

If some days you can simply put them on and other days you cannot bend at the waist, what changed in those few days was not the disc. It was the conditions the disc was sitting in.

Shape is hard to reverse. But there is often still room to work with on the conditions side. This connects to why the same low back pain calls for different treatment when the cause is different.

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)