Intra-articular gouty tophi of the knee: CT and MR imaging in 12 patients

Objective. To define the imaging characteristics of intra-articular tophi o f the knee. Design and patients. Twelve patients with intra-articular tophi in the knee were studied with routine MR imaging, gadolinium (Gd)-enhanced MR imaging, and CT over a 4-year period. There were Il men and one woman, 25-82 years of age (mean age 48 years). Four patients did not have a documented history of gout at the time of the MR examination. The diagnosis of intra-articula r tophi was provided by arthroscopy and histological examination (5 patient s), by microscopic study of joint fluid (5 patients), or by characteristic clinical, laboratory and imaging findings (2 patients). Results. In 15 MR examinations the tophi were located purely intra-articula rly in 10 knees. In the remaining five MR studies, periarticular soft tissu es or bone, or both, were involved. All the intra-articular tophi manifeste d low to intermediate signal intensity on both T1- and T2-weighted images. All five Gd-enhanced MR examinations demonstrated a heterogeneous periphera l enhancement. All 10 CT scans showed varying degrees of stippled calcifica tions within the tophi. The nature of the calcifications was confirmed on h istological examination in three patients. Conclusion. Presenting clinical manifestations of gout may relate to intraa rticular tophaceous deposits. Such deposits present as masses on MR images with low to intermediate signal intensity on both T1- and T2-weighted image s and a characteristic enhancement pattern following intravenous Gd adminis tration. These features relate primarily to internal calcifications, which are most evident on CT images. MR evaluation (including Gd administration) supplemented, in some cases, with CT scanning allows accurate diagnosis of intra-articular tophaceous deposits.