Why your feet are fine at nine and swollen by three, and how my patient stopped the swelling in three days

You may well recognise some of it.

Then she went through everything she had already tried, which is the same list I hear from nearly everybody. Legs up on the arm of the sofa every evening, pillows under her feet in bed, less salt, more water. An uncomfortable amount on good shoes, then more again on insoles to go inside them. And compression socks, worn twice, then into a drawer.

None of it had made the slightest difference to how her feet felt by the middle of the afternoon.

So I told her to do the one thing that would make it worse.

I told her what I told everybody in those days. Buy a pair of knee-high compression stockings and wear them daily.

She said no. She had tried them. Hot, a fight to get into, and they had done nothing at all. She looked straight at me and said there must be another way, and that if I could not tell her what it was, I ought to go and find out.

That stung. But she was my patient, so I went back to the beginning. What I found took two months, and it was not in anything I had been taught.

Pick up any compression sock ever made and the same idea sits underneath it. The pressure is firmest at the ankle, because the ankle is the narrowest part of the leg, so squeezing it should push the fluid upward.

It sounds sensible. It is what I was taught. And it is aimed at completely the wrong place.

Your ankle is not a pump. It is a doorway.

The real pump sits in the sole of your foot. There is a reservoir of blood held under your arch, written up by a French surgeon in the 1890s and named the venous sole. Every step, your arch flattens under your weight and springs back, and that movement squeezes the reservoir and pushes blood up through the ankle and into the leg.

So the arch does the pushing, and the ankle is only what the fluid travels through on its way out.

Which means clamping the doorway is the last thing you want to do. If the pump underneath has stalled and you tighten a band around the exit, you have not helped anything move. You have given it one more thing to get past.

But that alone does not explain why you are fine at nine and finished by three. That was the second thing we found.

Your arch is held in shape by soft tissue, not bone. And soft tissue that has carried you around for sixty years gets tired, the same as the rest of you.

In the morning, after a night off, it still springs properly. It flattens, it rebounds, and the pump underneath does its job. That is why your feet are fine at nine, and why you have spent years assuming nothing is wrong.

By the middle of the afternoon that arch has been flattened a few thousand times and it stops rebounding. It just stays down.

A flat arch is not a broken arch. It is a stalled pump. And a stalled pump means the fluid stops leaving your feet.

Which is when I realised both pairs in your drawer are working against you.

The long stockings get it wrong twice over. Their firmest pressure lands on the ankle, which is the doorway rather than the pump, and the rest goes into the calf, which is the last stage of the journey rather than the first. They are also hot enough that most women peel them off by lunchtime, and inside your shoe they are a flat tube that does nothing for the arch that actually stalled.

And the ordinary pair you have on right now is no better. A thin flat tube with one elastic band at the top. No structure under the arch, and that single band sitting exactly where the doorway is.

Those grooves in your legs at night are not a sign your socks are slightly tight. They are a dam, sitting on the one spot that needed to stay open.

So I went looking for something that did neither.

A cushioned panel under the arch, so it keeps flexing instead of lying flat all afternoon. Compression gentle and graduated rather than a hard band. Thin enough to breathe, so it is still on at four rather than in the drawer by one. Easy to pull on. And nothing left behind in the skin at night.

The strange part is that they were already sitting in a drawer in my own clinic.

We had been giving Archly to plantar fasciitis patients for about a year, purely for the arch support, because that is what they are built for. Then one of them mentioned in passing that her ankles had stopped swelling in the evenings. She had not thought it worth raising, because it was not what she had come about.

I turned a pair inside out, which is what I do with everything. And there it was.

Every single thing Jean and I had gone looking for, sitting in a drawer in my own clinic, being handed out for the wrong problem.

I gave her a pair that week.

She rang the clinic on the third day, which almost nobody does. She said she had taken her shoes off at six and her ankles still looked like her ankles.

A few months later she wrote to say she was back out in the garden after tea, and that she had started staying for her granddaughter's swimming lesson instead of waiting in the car. She sent a photo of her feet with it.

What she actually wrote was: "I can't believe it was my socks the whole time."

If it is both feet, and it gets worse as the day goes on, and worse still in the heat, and you have spent years quietly filing it under your age, I would like you to stop believing that last part.

Your arch is tired. It is not finished.

You should notice something the very first afternoon you wear them. Nothing dramatic. Just that four o'clock arrives and your feet have not gone heavy on you. It builds from there, because every day your arch spends supported is a day it is not being flattened for ten hours straight.

If nothing changes, you email them and send the socks back. Thirty days, no argument. Which is the only reason I am comfortable telling anybody to try something in the first place.