Report of ganglion cyst in the anterior cruciate ligament of a 6-year-old child.

BACKGROUND: Intra-articular ganglion cysts of the knee are extremely rare within the pediatric population. To our knowledge, only seven case reports have been published in the medical literature identifying pediatric patients with intra-articular cysts of the anterior cruciate ligament (ACL). Intra-articular cysts of the knee are a rare cause of knee discomfort and mechanical symptoms such as locking of the knee. To our knowledge, up until now the youngest patient reported in the medical literature with an intra-articular ganglion cyst of the ACL was a 7-year-old boy. CASE REPORT: We describe a 6-year-old boy who presented with a unilateral intra-articular ganglion cyst of the ACL in the right knee. In addition to the diagnostic work-up of radiographs and MRI, the cyst was successfully treated with arthroscopic resection and debridement to decompress the cyst. CLINICAL RELEVANCE: We provide a review of the proposed pathogenesis, diagnostic modalities, differential diagnosis, treatment options, and complications of treatment for intra-articular cysts of the ACL. LEVEL OF EVIDENCE: Level V, case report.