Ultrasound imaging for the rheumatologist XXXVI. Sonographic assessment of the foot in gout patients.

Objectives: This study aims to investigate the relationship between clinical and US findings together with the prevalence and distribution of US findings indicative of monosodium urate (MSU) crystal deposition within the foot in patients with gout.

Methods: A total of 50 patients with gout attending the in-patient and the out-patient clinics of the Rheumatology Departments were prospectively enrolled in this multi-centre study. Multiplanar examination of the following 15 joints was performed: talo-navicular, navicular-cuneiform (medial, intermediate and lateral), calcaneo-cuboid, medial, intermediate and lateral cuneiform-metatarsal, cuboid-4th metatarsal, cuboid-5th metatarsal and all five metatarsophalangeal (MTP) joints.

Results: The following US findings were indicative of gout: enhancement of the superficial margin of the hyaline cartilage, intra-articular tophus, and extraarticular tophus. In 46 patients, a total of 1380 foot joints were investigated. In 1309 joints that were not clinically involved, US detected signs indicative of joint inflammation in 9% (121/1309). Talo-navicular joint and the first MTP joint were the joints in which the highest number of US findings were found at mid-foot and fore-foot, respectively. At MTP joint level, dorsal scans allowed the detection of a higher number of US findings indicative of joint inflammation, and MSU crystal deposits rather than on the volar plane.

Conclusions: This study demonstrated that US detected a higher number of inflamed foot joints than clinical examination, and that the first MTP and the talo-navicular joints were the anatomic sites with the highest prevalence of US signs of MSU crystal aggregates.