Effect of Sex and Ankle Brace Design on Knee Biomechanics During a Single-Leg Cut

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Background: Despite success at preventing ankle sprain, prophylactics that restrict ankle plantarflexion motion may produce deleterious knee biomechanics and increase injury risk.

Purpose: To determine if ankle prophylactics that restrict plantar- and dorsiflexion motion produce changes in knee biomechanics during a single-leg cut and whether those changes differ between sexes.

Study Design: Controlled laboratory study.

Methods: A total of 17 male and 17 female participants performed a single-leg cut with 4 conditions: Ankle Roll Guard (ARG), lace-up brace, nonelastic tape, and an unbraced control. Peak stance knee flexion, abduction, and internal rotation joint angle and moment; total knee reaction moment (TKM) and its components (sagittal, frontal, and transverse); and ankle plantarflexion and inversion range of motion (ROM) and peak stance joint moments were tested with a repeated measures analysis of variance to determine the main effect and interaction of condition and sex.

Results: Brace and tape restricted plantarflexion ROM as compared with ARG and control (all P < .001). With the brace, women had increased peak knee abduction angle versus ARG (P = .012) and control (P = .009), and men had decreased peak knee internal rotation moment as compared with ARG (P = .032), control (P = .006), and tape (P = .003). Although the restrictive tape decreased inversion ROM when compared with ARG (P = .004) and brace (P = .017), it did not change knee biomechanics. Neither brace nor tape produced significant changes in TKM or components, yet sagittal TKM increased with ARG versus control (P = .016). Women exhibited less ankle inversion ROM (P = .003) and moment (P = .049) than men, while men exhibited significantly greater frontal TKM (P = .022) and knee internal rotation moment with the ARG (P = .029), control (P = .007), and tape (P = .016).

Conclusion: Prophylactics that restrict ankle plantarflexion motion may elicit knee biomechanical changes during a single-leg cut, but these changes may depend on prophylactic design and user’s sex and may increase women’s injury risk.

Clinical Relevance: Sex-specific ankle prophylactic designs may be warranted to reduce knee injury during sports.