Giulio Cocco, Vincenzo Ricci, Vito Cantisani, Andrea Delli Pizzi, Corrado Tagliati, Marco Di Serafino, Corrado Caiazzo, Gianfranco Vallone, Massimo Caulo, Antonio Corvino
Small post-surgical synovial hernias of the knee joint may represent a diagnostic challenge, given the limited sensitivity of physical examination for detecting these rare complications. We report the case of a 25-year-old woman with persistent anterolateral knee pain and swelling two years after anterior cruciate ligament reconstruction was performed arthroscopically. Compression and release of the transducer over the pathological sonographic finding, combined with the Doppler box, revealed a bidirectional flow signal at the level of the defect (positive Cocco sign), consistent with a post-surgical synovial hernia. The Cocco sign enhanced direct visualization of fluid displacement through a narrow fascial defect, supporting its role as a dynamic adjunct during the sonographic examination.