Photograph on left shows the position of the ultrasound transducer (on a patient in the prone position) for obtaining the image on the right. The gastrocnemius muscle is indicated by an arrow. Beneath the gastrocnemius is the semimembranosus bursa, which appears as a hypoechoic (fluid-filled) area marked by an asterisk. The semimembranosus is labeled; there is some hypoechoic change adjacent to the muscle, suggesting injury.
