Concurrent Synovial Chondromatosis and Pigmented Villonodular Synovitis of the Knee in a Pediatric Patient.

Synovial chondromatosis (SC) and pigmented villonodular synovitis (PVNS) are benign proliferations of the synovium of an unidentified etiology. This case report presents a rare case of PVNS of the left knee of a 4-year-old girl with intermittent pain and swelling diagnosed through preoperative imaging. Subsequent diagnosis of concurrent SC was made by arthroscopy and postoperative histological examination. To our knowledge, PVNS and SC are two distinct conditions that have never been reported as occurring simultaneously in the joint of a pediatric patient.