You Kneed to be Barefoot

There’s another study out on what most shoes do to feet, and specifically the stress that gets transmitted to the knees. Najia Shakoor, who’s been the lead investigator on other similar studies, Walking barefoot decreases loading on the lower extremity joints in knee osteoarthritis, and Effects of common footwear on joint loading in osteoarthritis of the knee, is also the lead investigator on this one.

It shows that training in what they call “mobility shoes” (designed to mimic barefoot walking) can lessen the stress on the knees even when regular shoes are then worn.

The new study is Improvement in knee loading after use of specialized footwear for knee osteoarthritis: results of a six-month pilot investigation.

It’s been known for a long time that common shoes exacerbate the effects (and may contribute to) osteoarthritis, due to the increased stress on the knee joints. I wrote about one of those studies in New Study on What Shoes do to Your Knees, and referenced other studies specifically on what high heels do, e.g., Women’s shoes and knee osteoarthritis. High heels increase the load by something like 30%.

What Dr. Shakoor’s studies have shown is that even “normal” shoes affect the gait, and increase the load by about 15% or so. What she did in this study was have the subjects wear the “mobility shoes” for six months, and see how it affected their gait.

First, let me say that the shoes have been described in other places as minimal shoes, or “minshoes”. That doesn’t mean that they were toed-shoes, like Vibrams. Here’s a picture of the mobility shoe used.

The Mobility Shoe

Here’s what the article says about it:

This specialized footwear is designed with sole cuts, or grooves, strategically placed at major flexion points of the foot, which allows the shoe to bend at areas where the foot would naturally bend during barefoot gait.

I think a lot of us would have preferred to see the study have the subjects for barefoot for the six months, but somehow I suspect they would have had a lot of study dropouts if they’d done that—so many people are so addicted to the thought of shoes.

Anyways, they tracked the stress on the knees (actually, something called the “knee adduction moment”) for six months as the subjects wore the mobility shoes during most of their day. During the study, they regularly retested the subjects, having them don their old regular shoes for one test, the mobility shoes for another test, and barefoot for a final test.

Here is the main graph of their results:

Longitudinal changes in the peak external knee adduction moment

As you can see, barefoot was best. But using mobility shoes over that period brought even shoe-wearing down to what barefoot did at the beginning.

Obviously, what happened was that the subjects learned to walk differently in the shoes with the (mostly) flexible sole. That training even carried over into their barefoot walking, with their barefoot walking at the end also generating less stress than at the beginning of the study.

I think this does a good job of showing that fixed sole shoes (like dress shoes and running shoes), in which the foot is encased in shoe and unable to flex properly, screw up not just the encased feet but the whole gait.

But there is also something that this study was not able to get at, and that’s the full feedback and proprioception that comes from being fully barefoot. We barefooters are well-aware that direct feedback from the sole is also tremendously important in terms of placing our feet and allowing the body to work as a unit from our toes to our head. It would be really nice if they could repeat the study with the subjects really going barefoot over the six months. But I’m not holding my breath.

I’d also like to mention that the study also measured the subjective knee pain of the subjects. While I like the results (the more barefoot-like, the less knee pain), I’m also a bit suspicious of such a subjective measure. It’s nice to know but not definitive.

The authors of this study recognize that it is a fairly limited study. There was no control group. The measure of pain was subjective, with no double-blinding.

And while they showed that the mobility shoes improved gait even when the subjects wore their normal shoes, who knows how long that would last.

[T]he current study demonstrated that knee joint loads were reduced not only when participants wore the study mobility shoe, but also during natural barefoot gait, and knee joint loads even improved when participants walked in their original footwear over the 6-month period. These findings suggest that this noncustom footwear functioned as a biomechanical training device to beneficially alter gait mechanics. It is unclear how long these beneficial effects could be maintained if use of the footwear were discontinued, nor has the maximum potential loading reduction been defined yet, since the load-reduction trend appeared to be continuing at 6 months.

I may be biased, but I suggest that folks ought to just go barefoot all the time. 🙂