Synovial chondromatosis of the knee. A rare cause of knee pain in pediatric age

Synovial osteochondromatosis consists of a synovial metaplasia which affects 1 per 100 000 people. It is a very rare disease among children. It typically affects large joints of the body, especially the knee. Due to the lack of specificity of the signs and symptoms and X-Ray images, imaging tests such as nuclear magnetic resonance or computerized tomography are frequently needed for diagnosis. We report a case of a ten-year-old female patient with a six months history of pain and deformity of left patella which was diagnosed with synovial osteochondromatosis. This case highlights the importance of clinical suspicion, not only because it is an extremely rare disease in children, but also because it needs a surgical treatment as soon as possible in order to avoid consequences it might have in pediatric age, as joint destruction or malignization to chondrosarcoma.