Posterior ankle impingement syndrome: a diagnosis rheumatologists should not forget. Two case reports.

The ankle is a common site of painful symptoms in athletes and nonathletes. Posterior ankle pain can be the end result of several pathologies, and a diagnostic challenge for rheumatologists. The posterior ankle impingement syndrome, also known as os trigonum syndrome and posterior tibiotalar compression syndrome, is a clinical disorder characterized by acute or chronic posterior ankle pain triggered by forced plantar flexion, which causes chronic repetitive microtrauma. Pathology of the os trigonum-talar process is the most common cause of this syndrome, but there are other causes, such as tenosynovitis of the flexor hallucis longus, ankle osteochondritis, subtalar joint disease, and fracture. Diagnosis is based on clinical history and physical examination, and complemented by findings on plain radiography (RX), ultrasound (US), scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI). It is worth noting that RX has low cost and good sensitivity, US can provide guidance to therapeutic infiltrations, and MRI allows the assessment of surrounding soft tissues.