OBJECTIVE: To investigate postural control deficits and their correlation with recurrent ankle sprains in patients with both chronic ankle instability (CAI) and chronic syndesmotic injury (CSI). DESIGN: Cross-sectional design. SETTING: Motion laboratory and Orthopedic department. PARTICIPANTS: 73 individuals with CAI and 15 healthy controls Main outcome measures: Patients with CAI were divided into a CAI group (isolated CAI) and a CSI group (CAI with CSI) based on arthroscopic findings. Postural control was evaluated using the Sensory Organization Test, Adaptability Test, and Romberg Test. RESULTS: The CSI group had significantly lower somatosensory, visual, and vestibular scores and higher visual dependency compared to CAI group and controls (p <
0.05-0.001). CSI groups showed higher sway energy than the CAI in the plantarflexion sway (p <
0.05). Correlation analysis indicated strong associations between sprain incidence and plantarflexion sway energy (r = 0.68, p <
0.001), VAS scores (r = 0.54, p <
0.001), and somatosensory deficits (r = -0.43, p <
0.001). The AUC for the logistic regression model was 0.906, indicating excellent model performance (p <
0.001). CONCLUSIONS: Our results found that plantarflexion instability of the CSI correlates most strongly with the risk of ankle sprains, despite coexisting multisensory deficits. Hence, rehabilitation should address these deficits, pain management and targeted training.