# Pediatric intraarticular ganglion cyst with extraarticular extension in the knee: A case report

## TL;DR

A rare case of a knee ganglion cyst in a 5-year-old child with both intraarticular and extraarticular features is reported, highlighting its diagnosis and successful surgical treatment.

## Contribution

This is the first reported case of an infrapatellar fat pad ganglion cyst with extraarticular extension in a pediatric patient.

## Key findings

- The case describes a 5-year-old boy with a rare intraarticular ganglion cyst and extraarticular extension in the knee.
- Surgical excision via arthroscopy successfully treated the cyst with full recovery and no recurrence.
- Magnetic resonance imaging was crucial for diagnosis, and meticulous surgical planning was essential for treatment.

## Abstract

In total, there are fewer than ten reported cases of intraarticular ganglion cysts in the pediatric population. Herein, we report a rare case of intraarticular ganglion cyst inside the knee with extraarticular extension in a 5-year-old child.

A 5-year-old boy presented with an anterior knee mass associated with limping, and limited range of motion in the right knee for 1 year. Surgical excision with arthroscopy was performed to treat the intraarticular ganglion cyst with extraarticular extension. At follow-up, the mass had completely detached, and the patient had full range of motion without complaints or recurrence.

Ganglion cysts are benign lesions, and are extremely rare in pediatric age groups with fewer than ten cases reported in the literature. We report this case as the first infrapatellar fat pad ganglion cyst with anterolateral extraarticular extension via the lateral reticulum, compared to previous reported cases, which were pure intraarticular cysts the majority of which had an ACL origin.

The clinical manifestation of a rare ganglion cyst in the knee is variable. Magnetic resonance imaging is the cornerstone of diagnosis. Treatment varies according to the cyst location, and requires analysis of the mass, meticulous preoperative planning, and experienced surgeons.

•There are fewer than ten reported cases of intraarticular ganglion cysts in the pediatric population.•The clinical manifestation of a rare ganglion cyst in the knee is variable. Magnetic resonance imaging is the cornerstone of diagnosis.•Treatment varies according to the cyst location, and requires analysis of the mass, meticulous preoperative planning, and experienced surgeons.•The reported case is a rare intraarticular ganglion cyst within the knee with extraarticular extension in a 5-year-old child.•The ganglion cyst was excised through knee arthroscopy; the skin was incised along the anterolateral portal, which was approximately 1.5 cm in length, to excise the extraarticular extension of the cyst. Then, by utilizing the same incision, the arthroscope was used to fully extract the remnant intraarticular portion of the cyst

There are fewer than ten reported cases of intraarticular ganglion cysts in the pediatric population.

The clinical manifestation of a rare ganglion cyst in the knee is variable. Magnetic resonance imaging is the cornerstone of diagnosis.

Treatment varies according to the cyst location, and requires analysis of the mass, meticulous preoperative planning, and experienced surgeons.

The reported case is a rare intraarticular ganglion cyst within the knee with extraarticular extension in a 5-year-old child.

The ganglion cyst was excised through knee arthroscopy; the skin was incised along the anterolateral portal, which was approximately 1.5 cm in length, to excise the extraarticular extension of the cyst. Then, by utilizing the same incision, the arthroscope was used to fully extract the remnant intraarticular portion of the cyst