These problems came to a head when Benno Nigg published a now-widely-cited paper in 2001 detailing the evolution of his laboratory’s work on pronation and orthotics.
Nigg detailed a series of studies he carried out which illustrated that individual runners had differing responses to the same orthotic features.
Check this out:
While a reinforced arch and a slanted heel reduced pronation in some runners, others had little or no change, and some even exhibited increased pronation.
It get’s worse:
Using bone pins and X-ray imaging, Nigg and his colleagues found that there is little difference in skeletal movement between shoes with standard inserts, shoes with custom inserts, and no shoes at all!1
Several studies were showing a beneficial effect of custom orthotics.
A 1991 survey of 347 runners who used custom orthotics after suffering an injury found that 75% reported complete or near-complete recovery, and 90% continued to use their inserts after recovery.2
A more recent investigation in 2011 similarly found that custom orthotics reduced pain and were well-tolerated among most runners.3
The evidence when it comes to specific injuries is less clear—they might hasten recovery for example, but the overall recovery rate is similar between runners with knee injuries who receive custom orthotics and those who do not.4