Isolated Synovial Osteochondromatosis in a Completely Enclosed Suprapatellar Pouch: A Rare Case Report

A complete suprapatellar plica of the knee is a rare condition that separates the suprapatellar pouch from the rest of the knee cavity. Synovial osteochondromatosis is a rare benign monoarticular arthropathy affecting synovial joints that are clinically manifested as intra-articular multiple loose bodies. Isolated synovial osteochondromatosis within a concealed suprapatellar pouch caused by complete suprapatellar plica is an exceptionally rare occurrence. There is no well-documented report in literature on the diagnosis and arthroscopic approach to osteochondromatosis within a separated suprapatellar pouch. We report the case of a 61-year-old man who presented with a 3-month history of atraumatic right knee pain localized to the suprapatellar region. Pre-operative magnetic resonance imaging confirmed the presence of loose bodies at the suprapatellar region behind the complete septum. Loose bodies were concealed in a sealed suprapatellar pouch and could not be detected by routine arthroscopic examination of the knee cavity. The suprapatellar plica was punctured and loose bodies trapped within the enclosed suprapatellar compartment were arthroscopically removed. Histological examination of the loose bodies confirmed the diagnosis of osteochondromatosis. The patient postoperatively experienced complete relief of knee pain. Successful arthroscopic removal of loose bodies in the separated suprapatellar compartment requires careful study of pre-operative imaging and can effectively be performed throughthe standard anteromedial and anterolateral arthroscopic portals.