Synovial chondromatosis is a rare disease of unknown etiology. It usually occurs unilaterally in the large joints like the knee, but may occur in the shoulder, elbow, hip, ankle and temporomandibular joints. The disease is usually intracapsular, but can also be extracapsular on rare occasions. The diagnosis of synovial chondromatosis is given after an anamnesis, physical examination and radiographic examination. However, the diagnosis is obtained after histological examination of the synovial tissue. We report an unusual presentation of bilateral synovial chondromatosis in the knee joint, with both intra and extracapsular localization. never described in the literature. Although synovial chondromatosis is described as a benign disease, it can be very destructive and debilitating. These lesions can mimic a malignant tumor and present a diagnostic problem.