Extraarticular synovial chondromatosis: review of epidemiology, imaging studies, microscopy and pathogenesis, with a report of an additional case in a child.

A rare benign condition of uncertain etiology and pathogenesis, Synovial Chondromatosis (SC) is most often seen intraarticularly in adults but only a handful of cases have been reported extraarticularly in children. Symptoms and physical signs consist of pain, swelling, and osteoarthritic changes related to a mass effect. Here we discuss the case of a 9-year-old boy with documented SC of the knee and critically review the Epidemiology, Clinical Presentation, Gross Anatomy and Microscopic Histopathologic Features as well as the role of Imaging Studies in Diagnosis. In addition, this paper reviews Current Pathogenetic Concepts including the infrequent but distinct possibility of malignant transformation.