Ultrasound imaging for the rheumatologist. XXXI. Sonographic assessment of the foot in patients with rheumatoid arthritis.

OBJECTIVES: The aims of our study were to investigate the prevalence of ultrasound (US) abnormalities in the foot of patients with rheumatoid arthritis (RA) and to compare them with the clinical findings. METHODS: One hundred RA patients were enrolled in the study. Bilateral US examination of metatarsophalangeal (MTP) joints, proximal interphalangeal (PIP) joints, midfoot joints (talonavicular, calcaneo-cuboid, medial, intermediate and lateral navicular-cuneiform and cuneiform-metatarsal joints and cuboid-4th and 5th metatarsal joints) were examined for synovitis and erosion. In addition the plantar fascia and the insertion of the anterior and posterior tibialis and peroneous brevis tendons were imaged. RESULTS: Effusion with synovial proliferation was visualised only at MTP joints in 84 out of 200 (42%) feet, at MTP plus at least one joint of the midfoot in other 41 out of 200 (20%) feet (making a total of 125 out of 200 (62%) MTP joints) exclusively in one or more joints of the midfoot in 7 out 200 (3%) feet, in the PIP joint of the 2nd and 3rd toes in 3 (1.5%) and 4 (2%) feet respectively, while no effusion with synovial proliferation was visualised in the PIP joint of the 4th and 5th toes. Synovitis was present most frequently in the 2nd MTP joint whilst erosions were most frequently imaged in the 5th MTP joint. CONCLUSIONS: US examination appears to be a useful imaging technique to study joint and tendon involvement of the foot in RA patients. Moreover, US examination of the foot is more sensitive than clinical examination in the detection of joint inflammation and allows for a better understanding of the features and the progression of the disease.