The clash between theory and science on the kinematic effectiveness of foot orthoses.

Foot orthoses have been shown to be effective in the management of lower extremity pathologic conditions, but the mechanism by which orthoses achieve this effect is unclear. Kinematic studies that investigate changes in skeletal alignment from the use of foot orthoses have shown mixed results with generally small changes which may not be sufficient to account for the outcomes achieved with foot orthoses. A number of theoretic constructs have not been taken into account in the design and reporting of kinematic studies, and these omissions may account for mixed results. Kinematic studies need to report information about participants, (e.g., the subtalar joint axis position) so readers can judge the appropriateness of the orthoses prescriptions and the kinematic variable measured. The high prevalence of forefoot varus reported in some studies and the variability in orthoses prescriptions and in casting for these devices used in studies also needs to be addressed. In light of some of the theoretic explanations offered here, the recent suggestions that foot orthoses may work by methods other than aligning the skeleton may need to be re-evaluated.