Imaging of impingement lesions in the ankle.

Ankle impingement and instability are well-recognized complications of ankle sprain. Ankle impingement is an important cause of chronic ankle pain in active populations, particularly in the professional athlete. Depending on anatomical location and the structures involved, impingement syndromes are classified into anterolateral, anterior, posterior, posteromedial, and anteromedial types. Clinically, impingement syndromes are characterized by painful limitation of full-ankle movement. Ankle impingement results from repetitive subclinical trauma due to overuse injuries, which, in the subacute or chronic situation, lead to abnormal osseous and soft-tissue thickening within the ankle joint. Various imaging techniques can be used in the diagnosis of ankle impingement. Usually, radiography is the initial imaging technique performed to rule out bony trauma and identify potential anatomical bony abnormalities. Use of computed tomography and isotope bone scanning is largely superseded by magnetic resonance imaging, although with variable sensitivity and specificity. Arthrographic techniques, using computed tomography or magnetic resonance, are useful for exquisite demonstration of capsular recesses and synovial abnormalities. Imaging-guided injection techniques can be used in the management of impingement for pain ablation and to aid clinical diagnosis, especially in hind foot pain.