Background Due to the prevalence of ankle instability in active individuals, it is important to understand what characteristics patients with ankle instability exhibit during dynamic tasks. Appreciating differences in peak plantar pressures (PPP) during walking may provide insight to understanding why these patients suffer subsequent injuries.

Objective Measure PPP in 3 areas of the foot during walking in those with and without chronic ankle instability (CAI).

Design Case-control study.

Setting University biomechanics laboratory.

Participants 20 physically active participants were each assigned to the CAI group (20 ± 30 years; 173.61 ± 7.84 cm; 73.91 ± 17.58 kg), 20 and to the control group (20 ± 10 years; 169.90 ± 9.50 cm; 64.53 ± 14.01 kg).

Interventions At a self-selected speed, participants walked barefoot across Tekscan™ pressure mats, creating a footprint of peak pressure data. Using the Tekscan™ software, the footprint for the involved and matched control ankle was divided into 3 areas and PPP in each area were determined.

Main outcome measurements PPP in medial rear-foot (MRF), lateral rear-foot (LRF) and mid-foot (MF).

Results The MRF PPP was significantly higher (F = 5.25, p = 0.028) in those with CAI (Kpa² = 292.48 ± 40.72) compared with controls (Kpa² = 258.33 ± 59.79) during walking. There were no significant differences in the LRF or MF between the two groups (p > 0.05).

Conclusions This confirms previous studies which have demonstrated differences in plantar pressure of patients with CAI compared to controls. The increased medial rear-foot pressure may be the result of a protective strategy, avoiding inversion as a mechanism for subsequent injuries. More kinematic data should be collected to determine actual position of the foot at initial contact of walking gait.