Primary synovial chondromatosis of the ankle joint presenting as monoarthritis.

To cite: Santiago T, Mariano C. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2013202186 DESCRIPTION Synovial chondromatosis is a rare, benign condition characterised by the formation of multiple cartilaginous and osteocartilaginous bodies in the capsule. Synovial chondromatosis has been widely described in the literature. Most cases involve temporomandibular, shoulder, elbow, hip and knee joints. Interestingly, published cases with ankle joint involvement are uncommon. The rarity of this diagnosis in the literature spurred us to report our case of synovial chondromatosis of the ankle joint. The patient, a 42-year-old man, had a 2-week history of pain and swelling in his left ankle. On physical examination he had a decreased range of motion on dorsiflexion and in inversion/eversion of the ankle. A radiograph revealed soft tissue oedema surrounding multiple calcified loose bodies located at the anterior aspect of the left ankle (figure 1A). Because there was no history of direct ankle trauma or systemic inflammatory disease, primary synovial chondromatosis was strongly suspected. The patient underwent arthrotomy and surgical excision of the intra-articular bodies, and the diagnosis was confirmed (figure 2A–C). Histological examination revealed synovial chondromatosis with multiple osteocartilaginous fragments from the synovium. At 4 months postoperatively, the patient is asymptomatic with no evidence of recurrence on serial physical examination and radiography (figure 1B). Synovial chondromatosis is a rare, benign condition characterised by the metaplasia of synovial tissue and the formation of cartilaginous and osteocartilaginous bodies in the capsule.