Snapping Pes Anserinus Caused By Gracilis Tendon: A New Mechanism Proposed by Dynamic Knee Ultrasonography

Abstract

Snapping pes anserinus is the main extra-articular cause of snapping on the medial side of the knee. There are limited articles that describe the mechanism of the condition, especially only when flexion of the knee. We report a case of snapping pes anserinus in a 23-year-old skier, which was reproduced on only active flexion of both knees in the posteromedial aspect of the tibia, with pain for 6 years, diagnosed using dynamic ultrasonography for elucidating a new mechanism of the gracilis tendon. We performed dynamic ultrasonography of the right knee of the patient; the gracilis tendon was twisting and folding and then, snapping occurred when the gracilis tendon passed by the sartorius muscle. The atypical movement of the gracilis tendon was considered the primary factor for snapping in this patient, which was diagnosed with dynamic ultrasonography.

Keywords

• knee
• ultrasonography
• gracilis muscle
• tendons