More than 80% of musculoskeletal injuries among adults are related to physical activity, with 70% occurring in the lower extremity (10). The interdependency of the mechanics of the lower extremity joints (2) is known as the kinetic chain. As an example of this interdependency, excessive pronation of the foot (flatfoot) is likely a factor related to many leg, knee, and low back pathologies (3,13). The excessive pronation of the foot may cause the leg to internally rotate, resulting in knee valgus position, causing the pelvis to tilt anteriorly and laterally, ultimately affecting lumbar function (1,13). This mechanical sequencing affects the working length of the muscles, changing the effectiveness of force production capability (1). In addition, altered joint positions lead to increased load applied to static joint structures like ligaments and joint capsules (13,17). Another foot type, the more rigid supinated foot (“high-arched” foot) is associated with impact-related injuries like stress fractures as the impact attenuation capability is reduced because of reduced flexibility in the foot (12,17).
One reliable method of identifying foot types that may predispose individuals to injury is the arch ratio (9,17). The lower ratio (≤0.275) is considered “flat arch,” and individuals with this foot type would benefit from “motion control” shoes that include more arch support (5). A high-arch foot type (ratio, ≥0.356) would benefit from shoes that provide additional cushioning (7).
Another relatively new method of assessing the dynamic function of the body to predict injury is functional movement screening (FMS) (6). FMS includes seven dynamic movement tasks that are scored individually using a three-point scale; 3 being the most functionally sound (the composite score is 21). An individual scoring a perfect 21 would be less likely to suffer an injury while someone scoring below 21 may be more likely. The intervention to potentially prevent injury would be specific for the test in which the individual did not score well. For example, an individual with a low score on shoulder mobility may benefit from shoulder flexibility training. High intratester and intertester reliabilities have been reported for this screening method, even among novice testers (16). Studies of NFL football players have identified the preseason composite score of 14 as the cutoff for increased injury prevalence during the season (11,15). However, the cutoff value for heightened injury risk seems to be dependent on the population tested (4,14,15).
Some biomechanical characteristics have been identified to have association with certain musculoskeletal injuries, and clinicians can perform screening tests to recognize these characteristics. The complexity in human body movements will continue to be a challenge in identifying clear mechanical features that have causal effects on injuries.
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