How can a ganglion cyst be differentiated from a parameniscal cyst on Ultrasound?
Ganglion cysts may have a variety of appearances at US, but are noncompressible, are in close proximity to a tendon or joint, and do not have vascularity on Doppler imaging. Large ganglion cysts, defined as greater than 10 mm, often demonstrate the classic anechoic mulilobulated or multiloculated appearance with increased through transmission. However, small ganglion cysts, defined as less than 10 mm, often do not appear as simple cystic lesions but instead are hypoechoic without posterior acoustic enhancement. When attempting to differentiate a ganglion cyst from a cyst arising from fibrocartilage (paralabral or parameniscal), location is the key. Fibrocartilage cysts should be in contact with the labrum or menisci, while ganglion cysts are often located at the sinus tarsi in the ankle, superficial to the scapholunate ligament or near the radial artery in the wrist, or within Hoffa’s (infrapatellar) fat pad of the knee.