Snapping Pes Anserinus and the Diagnostic Utility of Dynamic Ultrasound

Snapping pes anserinus syndrome is an often encountered cause of medial knee snapping. It results from impingement and translation of the gracilis tendon or semitendinosus tendon over the osseous structures of the knee during active flexion and extension. Ultrasonography is often the diagnostic imaging test of choice in cases of mechanical snapping. We report 2 cases of painful snapping pes anserinus and highlight the value of dynamic ultrasound in making an accurate diagnosis so as to direct care.