Do corrective shoe inserts work the way we think they do?
A new study in the Journal of Applied Biomechanics found that orthotic insoles, often recommended to flat-footed athletes with patellofemoral pain syndrome, or “runners knee,” don’t actually affect knee and hip mechanics, reported Runner’s World.
However, they do, inexplicably, work.
Doctors often tell flat-footed runners to get insoles to correct over-pronation—the added inward roll of a flat foot striking the ground—and the reason seems to be obvious: as the foot rolls inwards, it causes additional stress on the ankle and connecting musculature all the way up to the knee and hips.
Prevent the roll with an orthotic wedge, the conventional wisdom says, and prevent the extra stress on your joints.
Not so, apparently.
The researchers studied 20 women with runner’s knee and 20 without, all of whom run at least ten miles a week. They were all given the same model of New Balance running shoes and asked to run with and without orthotic inserts.
The subjects were then filmed using 3D motion sensors that allowed the researchers to analyze the runners’ biomechanics in detail. What they found was an insignificant difference in those biomechanics—specifically knee and hip angles—between any group.
In short, there was no major difference with or without the inserts, regardless of the runner’s state of injury.
And yet, the authors point out, other studies indicate that insoles still seem to reduce knee pain and increase recovery time. The reasons, they suggest, may have to do with the angle of the wedge or foot mechanics inside the shoe, which can’t be tracked by camera.
But as of right now, why those wedges work remains a mystery.