The effect of ankle bracing on kinematics in simulated sprain and drop landings: a double-blind, placebo-controlled study

Key points

1. 01Only the active brace reduced inversion angles during sudden inversion; the placebo brace performed no differently from unbraced
2. 02No placebo effect was detected for ankle bracing in patients with a history of lateral ankle sprain
3. 03The protective effect appeared between 65 and 140 milliseconds after the initial inversion
4. 04Neither brace altered sagittal plane ankle or knee kinematics during single-legged drop landings
5. 05Brace design matters: frontal-plane restriction without sagittal restriction may be ideal for high-impact sports

How it was conducted

Design

Double-blind, placebo-controlled, repeated measures laboratory study

Participants

16 adults with a history of unilateral lateral ankle sprain (7 female, 9 male; mean age 30.9 years)

Conditions

Active brace (dilatant fluid module resisting high-velocity inversion), passive placebo brace (identical appearance, no resistance module), and unbraced

Tasks

Single-legged drop landings from 0.2 m and sudden inversion tilt perturbations at 400 deg/s and 150 deg/s

Primary outcome

3D ankle inversion angle and sagittal knee and ankle kinematics measured by motion capture

Analysis

Repeated measures ANOVA with statistical parametric mapping (SPM) across the full time series

What they found

• Active brace vs. unbraced: significant reduction in inversion angle between 65 and 140 milliseconds after initial drop (P < .001) and between 180 and 200 milliseconds (P = .013)
• Passive placebo brace vs. unbraced: no significant differences in inversion angle at any time point during the drop
• Slow tilt (150 deg/s): no significant differences across all conditions
• Drop landing sagittal ankle angles: SPM{F} did not exceed critical threshold of 4.646; no significant differences among conditions
• Drop landing sagittal knee angles: SPM{F} did not exceed critical threshold of 4.524; no significant differences among conditions
• Active brace reduced maximal inversion angle by approximately 5 degrees compared with unbraced, comparable to a 3-degree reduction reported by Tang et al. with an Aircast brace

Limitations

• Small sample of 16 participants limits statistical power and generalisability
• Time since initial lateral ankle sprain varied across participants, introducing heterogeneity
• Muscle activity (EMG) was not assessed, so compensatory neuromuscular changes cannot be excluded
• Mean participant age of 30.9 years is higher than many comparable studies, which may limit direct comparison

Why it matters

For patients

Athletes with a history of ankle sprain can expect a well-designed active brace to mechanically limit dangerous inversion without restricting normal running and landing movements.

For clinicians

Brace selection should prioritise designs that restrict only high-velocity frontal plane motion; placebo confidence does not appear to drive the protective effect in this population.

For readers

This study provides controlled laboratory evidence that the mechanical properties of a brace, not the mere act of wearing one, account for reduced inversion during a simulated sprain.