Snapping Knee Caused by a Superiorly Displaced Medial Meniscus: Knee Dynamic Ultrasonographic Findings.

The causes of snapping knee include meniscal instability, but dynamic ultrasonographic findings have rarely been reported. Here, we report a case of snapping knee due to direct trauma to the right knee of a 79-year-old woman. Dynamic ultrasonography is used to confirm the snapping phenomenon caused by the anterosuperior displacement of the truncated posterior horn and body of the right medial meniscus.