Wrisberg-variant discoid lateral meniscus: current concepts, treatment options, and imaging features with emphasis on dynamic ultrasonography

Discoid lateral menisci represent a range of morphologic abnormalities of the lateral meniscus. The Wrisberg-variant discoid lateral meniscus is an unstable type that lacks posterior ligament attachments, resulting in "snapping knee syndrome." Abnormally mobile discoid lateral menisci are difficult to diagnose both clinically and with traditional static imaging, such as magnetic resonance imaging. In this article, we discuss the pathophysiology, clinical features, imaging findings, and treatment options for Wrisberg-variant discoid lateral menisci. We focus on the role of dynamic ultrasonography in revealing lateral meniscal subluxation during provocative maneuvers.