Synovial chondromatosis is a rare pathology of unknown aetiology. It originates from the chondroid metaplasia of the connective tissue of the synovial membrane. Consequently, cartilaginous nodules develop in the affected joints, first calcifying and then ossifying. The bursae mucosae, the vaginae tendinis and the para-articular connective tissue are less frequently affected. The most common locations of this pathology are the knee, the hip, the shoulder, the elbow and the ankle. The small joints are rarely affected, even less the bilateral involving of joints, above all of hand or foot, is exceptional. In a clinical and radiological valuation, it is difficult to distinguish synovial chondromatosis from osteoarthritis and from degenerative arthopathies in general. A sure diagnosis can be obtained only by means of a histological examination. We here report a case of synovial chondromatosis bilaterally located on the first metatarsophalangeal joint. Clinical and radiological features were similar to those of hallux rigidus, a typical and peculiar metatarsophalangeal joint pathology. The diagnostic suspicion arose during surgery, and was subsequently confirmed by histological examination. During the following visits, the patient did not present any painful symptomatology.