Clinical History
50 year old man with uncomfortable snapping sensation along the medial aspect of the right knee upon flexion and extension.
Diagnosis: Snapping of the Sartorius Tendon over a Medial Parameniscal Cyst
Sonography is the supreme imaging modality for evaluating superficial soft tissue snapping due to its soft tissue resolution and ability to capture dynamic motion in real time.
If the patient can localize the snapping sensation and reproduce it, the probe can be placed in the region of interest to evaluate for structural abnormalities as well as for abrupt snapping of structures across each other.
Though the meniscus is not well seen on ultrasound due to deeper location within the knee joint, a parameniscal cyst emanating from a meniscal tear is easily visible, in this case, along the path of motion of the sartorius tendon which snaps over it upon active knee flexion and extension.