T he human foot is often classified into 3 structural categories: high, normal, and low arch, based on its anatomical alignment 89 and the height of the medial longitudinal arch. 27 Classification in these 3 categories is typically based on cutoff values determined from the distribution of data (standard deviations 65,93,102 or percentiles 15,16 ) from measurements taken on a large population. The interest in such classification is the belief that nonneutral foot morphology, such as a high or low arch (flatfoot), may lead to less than optimal foot function and be associated with the development of lower extremity and low back injuries. 23,28,29,59 A review of the literature provides conflicting evidence on the potential relationship between foot type and lower extremity injuries. Although a number of published reports have found no relationships between nonneutral foot types and lower extremity injuries, 40,94,96,99 the authors of a recent systematic review concluded that both high-and low-arch foot types were associated with runningrelated injuries. 14 The results of this systematic review, 14 which did not include a meta-analysis and effect-size estimates, contrast those of a few qualitative reviews that failed to demonstrate a relationship between foot type and future lower extremity injuries. 4,8,20,70 This lack of consensus in the literature could be attributed, in part, to the variation in the operational definition of foot type among investigators. 4,70 A large variety of methods have been developed to classify the foot based on structure and alignment. These
T T OBJECTIVES:To investigate the association between nonneutral foot types (high arch and flatfoot) and lower extremity and low back injuries, and to identify the most appropriate methods to use for foot classification.
T T METHODS:A search of 5 electronic databases (PubMed, Embase, CINAHL, SPORTDiscus, and ProQuest Dissertations and Theses), Google Scholar, and the reference lists of included studies was conducted to identify relevant articles. The review included comparative cross-sectional, casecontrol, and prospective studies that reported qualitative/quantitative associations between foot types and lower extremity and back injuries. Quality of the selected studies was evaluated, and data synthesis for the level of association between foot types and injuries was conducted. A randomeffects model was used to pool odds ratio (OR) and standardized mean difference (SMD) results for meta-analysis.
T T RESULTS:Twenty-nine studies were included for meta-analysis. A significant association between nonneutral foot types and lower extremity injuries was determined (OR = 1.23; 95% confidence interval [CI]: 1.11, 1.37; P<.001). Foot posture index (OR = 2.58; 95% CI: 1.33, 5.02; P<.01) and visual/ physical examination (OR = 1.17; 95% CI: 1.06, 1.28; P<.01) were 2 assessment methods using distinct foot-type categories that showed a significant association with lower extremity injuries.
