Ganglion cyst of the anterior cruciate ligament in children.

The incidence of ganglion cysts of the anterior cruciate ligament (ACL) has increased significantly since the advent of MRI, but it remains exceptional in children. We report the case of a 7-year-old boy, with an exceptional imaging exam and histological finding of a ganglion cyst. The lesion was at first an MRI finding with a hypointensity signal on T2-weighted sequences of a normal ACL. An arthroscopy was performed that showed a cyst measuring 40 mm filling the intercondylar notch and involving the roof and the edges of the ACL. A cystography confirmed the position of the cyst, which was removed with specific management of the ACL. Histological examination confirmed the absence of mucoid degeneration, which is always observed in adult lesions. We believe that the ganglion cyst of the ACL in children differs in pathogenesis from common degenerative cyst in adults.