A 69-year-old, right-handed, man living in a rural area and formerly employed by the textile industry was referred by a physician to the department of trauma and orthopedic surgery of our University Hospital with a 2-year history of progressive swelling and pain of the left hand. The patient had been in repeated contact with animals but had no history of tuberculosis, rheumatic disease, joint trauma, or infectious disease. In the physical examination, a soft mass of the left thenar eminence measuring 2 x 5 cm, with no sign of local inflammation, was found (Fig. 1). Wrist and hand motion were preserved. He presented paresthesia in the median nerve territory. We suspected an infectious or rheumatic disease, and a tumor was not excluded. Laboratory data, including complete blood count, erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, antinuclear antibody, and anti-cyclic citrullinated protein antibody, were normal. Brucellosis serology and a tuberculin reaction test were negative, and a chest radiogram was normal. Radiography showed a soft-tissue mass shadow without any apparent calcification (Fig. 2). Magnetic resonance imaging showed a regular thickening of the finger flexor sheath on both sides of the carpal tunnel measuring 25 x 45 mm with multiple rice bodies (Fig. 3). The radiological diagnosis was synovial chondromatosis. One week later, the decision to perform exploratory surgery was made. The patient was placed in a supine position with the left upper limb on a support. Then, surgical exploration was performed under loco-regional anesthesia. A 10-in. curved incision was made on the ulnar side of the thenar crease, the presence of multiple rice bodies was noted visually. The rice bodies were removed, and a thorough excision of the sheath was performed, respecting the neurovascular structures. The carpal tunnel was also released (Fig. 4). Histopathological examination revealed a chronic non-specific synovitis, and results of culture and PCR for tuberculosis were negative. The surgical treatment allowed us to relieve the patient's symptoms without additional medical treatments, and his recovery was uneventful without any postoperative complications. The patient regained good function after 4 months (Fig. 5). One-year follow-up revealed no underlying disorder.