Ultrasound of the distal tibiofibular syndesmosis.

Purpose: To review the anatomy, biomechanics, ultrasound technique, and imaging features of the distal tibiofibular syndesmosis, and to highlight the role of ultrasound relative to MRI in evaluating syndesmotic injuries. Methods: A literature-based narrative review was performed, focusing on normal and pathologic ultrasound findings of the syndesmotic ligaments and their MRI correlation. Results: The anterior inferior tibiofibular ligament is the most commonly visualized and injured structure. It is best seen in an oblique axial plane, extending from the tibial to the fibular tubercle. It appears as a thin, well-defined, fibrillar, echogenic band crossing the syndesmotic interval. The posterior inferior tibiofibular ligament is best seen posteriorly, slightly deeper and thicker, extending between the posterior tibia and fibula. Ultrasound examination of acute ligament injury shows ligament thickening, loss of normal fibrillar pattern, fiber discontinuity, or the presence of small, avulsed bone fragments. Ultrasound of chronic ligament injury shows thinning, irregularity, or heterogeneous scarring. Hypoechoic fibrotic changes or calcification at insertion sites can also be seen. Ultrasound provides high-resolution, real-time imaging capable of detecting ligament tears and assessing tibiofibular instability under stress. Dynamic ultrasound demonstrates good correlation with MRI for identifying acute syndesmotic disruptions, particularly in athletic or acute trauma settings. Conclusion: Ultrasound is a valuable and accessible modality for evaluating distal tibiofibular syndesmotic injuries. It complements MRI by providing immediate, functional assessment, aiding in timely diagnosis and management of high ankle sprains. Ultrasound should be considered in the imaging algorithm for suspected syndesmotic injuries, especially in sports and trauma settings.