This study aimed to compare plantar pressure during walking between healthy subjects and patients with severe CLAI who required surgical treatment. The main findings were that patients with severe CLAI applied a significantly higher peak pressure on the medial aspect of the foot and lower peak pressure on the hallux and toes while walking than did healthy subjects. Interestingly, these findings were not consistent with those of previous studies involving participants with CLAI [9–11]. However, the participants with CLAI in previous studies did not require ankle stability surgery (i.e., their condition was less severe), which may explain why the plantar pressure differed from that in this study.
We observed higher pressure distribution in the medial aspect of the foot in patients with CLAI, which could have stemmed from a compensatory mechanism to avoid lateral ankle instability. This finding was also inconsistent with those of previous studies [9–11]. Feger et al. reported that the percentage of activation time of the peroneus longus muscle was greater in the CLAI group than in the control group . Moisan et al. reported that the muscle that seemed the most affected among participants with CLAI was the peroneus longus while walking . Due to the influence of the peroneus longus muscle, the peak pressure on the medial aspect of the foot is be higher, which contributes to the prevention of lateral ankle sprains.
Lower pressure in the toes and the hallux in patients with severe CLAI was observed in the current study, but Koldenhoven et al. did not report a significant difference in the pressure on the hallux between patients and controls . This contrasting finding could be explained by the avoidance mechanism of lateral ankle instability. The moment arm of the inversion force on the ankle joint that is generated by lateral thrust increases as the body weight shifts forward. Patients with CLAI may have unconsciously attempted to minimize the moment arm of the inversion torque on the ankle joint by reducing the peak pressure on the hallux and toes.
The limitations of this study should be considered. First, the plantar pressure was measured only once, the day before surgery, but the planter pressure pattern may change with time. However, because the evaluation was conducted immediately before surgery, the data could presumably be taken under the worst condition of CLAI. Second, patients with CLAI were slightly younger and slightly heavier than the control group. However, the activity level was similar, and all pressure data were normalized as their BMI was 22. Therefore, the statistical comparisons were scarcely affected. Lastly, although statistical significance was achieved in the comparisons, the current study participants might have been too homogeneous to apply the results to the other cultural and racial backgrounds. Thus, the generalizability of the results is limited. It should be noted that the current results were collected from subjects who were relatively older than most active sport athletes. Regardless, the current findings could be used to elucidate the biomechanical pathophysiology of CLAI. In addition, evaluating the plantar pressure after arthroscopic lateral ligament repair may contribute to the improvement of gait balance and gait posture, which may help to prevent the ankle from giving way.