Bilateral Knee Synovial Chondromatosis in a 2-Year-Old Girl: First Reported Case and Literature Review

BACKGROUND Synovial chondromatosis (SC) is a rare monoarticular benign condition characterized by the development of intra- or periarticular cartilage-like nodules or loose bodies. Typically affecting middle-aged men, SC is exceptionally rare in female pediatric patients. Symptoms include diffuse pain, swelling, and limited joint movement. The loose bodies are typically numerous, small, rounded, and uniform in size. Histologically, they consist of hyaline cartilage-like nodules containing clusters of chondrocytes. Bilateral SC in the knee of young children is even rarer and has not been previously documented in the medical literature. CASE REPORT A 2-year-old girl presented with recent pain in her right knee without preceding trauma. Physical examination revealed joint effusion, a limping gait, and limited knee flexion, with no signs of local inflammation. Radiographs showed normal joint structures, and laboratory test results, except for an elevated CRP, were normal. Joint aspiration ruled out septic arthritis. The worsening of symptoms within a relatively short period prompted further investigation, leading to the identification of numerous cartilaginous nodules within the joint during exploratory arthrotomy. Microscopic examination revealed unossified cartilage-like nodules containing disorganized chondrocytes. Four months after surgery, she was diagnosed with SC in the contralateral knee. CONCLUSIONS Given the rarity of synovial chondromatosis in young children, and the even rarer bilateral presentation in a large joint, this case report provides an opportunity to explore the challenges in diagnosing and managing such conditions in pediatric patients. To the best of our knowledge, this is the youngest reported case of bilateral SC of the knee in a pediatric patient.