Decoding imaging in ankle impingement: a comprehensive review

Ankle impingement syndromes comprise a heterogeneous group of osseous and soft tissue pathologies caused by abnormal contact between articular or peri-articular structures, resulting in chronic pain and restricted motion. They are anatomically classified into posterior compartment (posterior proper and posteromedial), anterior compartment (including anterior proper, anterolateral and anteromedial), and extra-articular lateral hindfoot impingement (ELHFI). Posterior impingement is most commonly related to os trigonum or a prominent Stieda process, with MRI demonstrating marrow edema and posterior soft tissue hypertrophy, while ultrasound enables dynamic assessment and image-guided intervention. Anterior impingement results from repetitive microtrauma leading to osteophyte formation and capsular fibrosis; radiography and CT depict osseous abnormalities, whereas MRI and ultrasound characterize associated soft tissue changes. Anterolateral impingement and anteromedial impingement are typically post-traumatic, with fibrosis and ligamentous injury within the joint recesses, best evaluated on MRI, and ultrasound providing dynamic assessment. ELHFI is an under-recognized entity associated with posterior tibial tendon dysfunction and medial arch collapse, resulting in talocalcaneal or subfibular impingement. Weight-bearing radiographs and CT assess hindfoot alignment, while MRI delineates tendon, ligamentous, and marrow abnormalities. Ultrasound plays an adjunctive role in evaluating tendon pathology and guiding interventions. This review summarizes current evidence on the imaging features, pathomechanisms, and management of ankle impingement syndromes, with particular emphasis on extra-articular lateral hindfoot impingement. It emphasizes the value of a multimodality imaging approach and underscores the evolving role of ultrasound in both diagnosis and management, supporting its integration as a frontline modality in appropriately selected clinical and interventional settings.