Magnetic resonance imaging of pigmented villonodular synovitis in subtalar joint. Report of a case.

Pigmented villonodular synovitis (PVNS) is rare in the foot; however, it developed in the subtalar joint extending around the ankle of a 24-year-old man. The diagnosis was made by a combination of clinical findings, most notably the aspiration of the synovial fluid. Magnetic resonance imaging was most useful in showing the extent of the soft-tissue mass before surgery. Low-signal intensity of the mass, featured on both T1- and T2-weighted images, was suggestive of PVNS.