Evolution of foot orthotics--part 2: research reshapes long-standing theory.

OBJECTIVE To challenge casual understanding of the causal mechanisms of foot orthotics. Although the classic orthotic paradigm of Merton L. Root and his colleagues is often acknowledged, the research attempting to explain and validate these mechanisms is far less clear in its appraisal. DATA SOURCES Studies evaluating the relationship of foot type (medial arch height) and use of foot orthoses to the motions of the foot and ankle were compared and contrasted. A search was conducted to evaluate other possible mechanisms of orthotic intervention. RESULTS Although Root's methods of foot evaluation (subtalar neutral position) and casting (non-weight-bearing) are well referenced, these methods have poor reliability, unproven validity, and are, in fact, seldom strictly followed. We challenge 2 widely held concepts: that excessive foot eversion leads to excessive pronation and that orthotics provide beneficial effects by controlling rearfoot inversion/eversion. Numerous studies show that patterns of rearfoot inversion/eversion cannot be characterized either by foot type or by orthotics use. Rather, subtle control of internal/external tibial rotation appears to be the most significant factor in maintaining proper supination/pronation mechanics. Recent evidence also suggests that proprioceptive influences play a large, and perhaps largely unexplored, role. CONCLUSIONS Considerable evidence supports the exploration of new theories and paradigms of orthotics use. Investigations of flexible orthotic designs, proprioceptive influences, and the 3-dimensional effects of subtalar joint motion on the entire kinetic chain are areas of research that show great promise.