Your knee clicks. That is not a countdown.

Feel-good Friday

My left knee clicks on the third stair from the bottom. Every single time.

Carol says she can tell which stair I am on from the kitchen. She is not wrong. There is a click on the third one from the bottom, a duller one near the top, and they have both been there for two years.

For a long time that sound worried me more than the ache did. An ache is a feeling. A click sounds like machinery. I had it in my head that every click was a bit more cartilage gone, and that I was counting down to a new knee.

So this week I went and read what the noise means. It was the most cheerful hour of reading I have had in a while.

First, how common it is

A team led by Adam Culvenor gathered 103 studies from 28 countries for the British Journal of Sports Medicine. Between them those studies covered 36,439 people and 41,816 knees. That is a lot of listening.

In ordinary middle-aged and older people, 41% had a noisy knee. Among those with no pain and no history of injury at all, it was 36%.

Read that second number twice. More than a third of people with nothing whatever wrong still creak.

Noise is more common in a worn knee, mind. Of people with knee osteoarthritis, 81% had it. But you can see the trouble with reading that backwards. If a third of sound knees click too, your own click cannot tell you which group you are in.

Then, whether it predicts anything

That is the better question, and somebody asked it properly. One study followed 3,495 older adults for four years and watched who went on to develop painful knee arthritis.

Two thirds of the people who said they always had a noisy knee did not develop it. Not in four years.

So the sound is a poor fortune teller.

And nobody can tell you for certain what it even is. There are three candidates: rough cartilage passing over cartilage, a tendon sliding over bone, or small gas bubbles collapsing in the joint fluid. The honest answer is that the evidence is not in yet.

Which brings me to Dr Donald Unger. He cracked the knuckles of one hand, and only that hand, for about sixty years… then compared the two. No difference. It won him an Ig Nobel prize in 2009, and it is still my favorite piece of research on joint noise.

Anyway, that is the week on knees… and it comes to four plain things.

Cartilage has no blood supply of its own. It feeds on movement, which is why your first ten minutes are the worst ten minutes. A tai chi class in a church basement held its own against a course of physical therapy across a full year. And stairs ask about three times as much of the knee as flat ground… so a hand on the rail is not cheating.

And a knee that clicks is, most of the time, just a knee that clicks.

Not one of those four told you to sit down. That is the part I would have most liked to hear two summers ago, on the floor of my bedroom, with a green tackle box still sitting out on the dock.

One tap below decides where we start on Monday. It is the only vote that matters here.

Here is to a noisy, easy weekend,
Walt