The Swelling Has Gone Down, but It Still Feels Stiff

"The swelling has gone down, but it still feels stiff."

I hear this a great deal after an injury. On the outside it looks fully healed, but inside it feels heavy and thick. This is not a mistaken thing to say. There is a reason it feels that way.

The body notices before it repairs

When something has gone wrong, the first work the body does is not repair. It is noticing. Marking the place where the trouble is comes first, and the response comes after that.

And the basic form of that response is inflammation. Inflammation is not the name of a disease but the name of a method the body uses.

Redness, swelling, and warmth are one piece of work

At an injured place four things come at once. It turns red, it swells, it grows warm, and it hurts. It feels as though several places have broken down at the same time, but that is not so. Most of it is the outward look of one piece of work.

That one piece of work is this. Send more blood to that place.

Blood holds the cells that take charge of immunity, and the various components carried in plasma. These have to be carried to the place where the trouble is, so the body widens the road.

• The slender arteries running there open → blood gathers, so it turns red and grows warm
• The walls of the capillaries grow loose → plasma leaks out into the tissue, so it swells

Redness, warmth, and swelling — these three are not things that happen separately. It is because blood passing through in quantity and at speed is itself what makes the vessel wall soft. What it means is that a place where blood flow has risen looks like that from the outside.

Pain, though, is somewhat different. There is a share that comes from being pressed by the swelling, but a larger share lies elsewhere. A few signalling substances that come out at the injured place lower the threshold of the nerve endings. That is why a stimulus that would ordinarily be nothing comes to hurt.

So pain is not a by-product of the swelling but a device switched on separately. This story comes up again further on.

Where recovery falls behind is the other side

The sending the body does well by itself. The side that falls behind is the work of gathering back what was sent.

The fluid that leaked out pools between the tissues. This is called interstitial fluid. This fluid does not go straight back into the vessels it came from. A considerable share is taken up slowly through the lymphatic vessels.

Here is what matters. The visible swelling going down and the fluid between the tissues being fully cleared are not the same thing. Even when the outside has settled, fluid may still remain between the tissues.

That state is the stiffness. While fluid remains, the pressure between the tissues stays high, and that pressure in turn presses on the lymphatic vessels and the small vessels and makes the gathering slower still. The side that was falling behind falls further behind.

"The swelling has gone down, but it still feels stiff" is, for that reason, an accurate observation.

So where is the work done

There are two things to do at this place. Evening out the sending of blood so that it does not go too far, and opening a way for the increased fluid to leave. Both have to be done together. Press only on the sending side and the repair is delayed; hurry only the gathering side and it backs up.

That the method of raising a sweat has long been used touches on this very point. A sweat is not only a lowering of heat but one of the ways of moving increased fluid out of the body. When fluid leaves and the pressure between the tissues comes down, the lymphatic vessels and capillaries that had been pressed do their work again.

The way a single dose of medicine does this work is interesting. The medicinal materials each take charge of a different place. One evens out blood that has gathered to one side, one adjusts the very signals that open and close the vessels, one supplies the material that forms the groundwork of the tissue. And for that device switched on separately spoken of earlier — returning the lowered threshold of pain — there is yet another that takes that share.

The places they touch differ and the force they push with differs, yet the result goes in one direction. Because the sending side and the gathering side have to be handled together, no single thing will do it.

Where this story continues

How the pressure between the tissues comes to the hand I have written down in What You Can Tell by Laying a Hand on the Belly.

How the body works out where the trouble is and where it sends the signal up is in Your Back Hurts, and I Look at Your Foot. If that piece is a story about the noticing side, this one is a story about what happens after the noticing.

When to see a doctor first

If one leg or one arm suddenly swells where there was no injury, if a fever comes along with a red patch spreading, or if swelling stays as it is for weeks — before a story like this, examination and testing come first.

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Sources

• A review setting out that rising blood flow and loosening vessels are one connected thing — Upsala Journal of Medical Sciences, 2015
• A review setting out how the lymphatic vessels gather up fluid pooled between the tissues, and how swelling remains when that gathering backs up — Clinical Science, 2023

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