Ultrasound imaging for the rheumatologist XXXV. Sonographic assessment of the foot in patients with osteoarthritis

Objective. The aims of our study were to investigate the prevalence of ultrasound (US) abnormalities in the foot of patients with osteoarthritis (OA) and to compare them with clinical findings. Methods. Consecutive patients with foot OA were investigated by clinical and US examinations. Bilateral US of the midfoot and forefoot joints was performed by using a Logiq9 machine, equipped with a multi-frequency linear probe, operating at 14 MHz; in addition, power Doppler was applied (frequency 7.5 MHz; gain 50%; PRF 750 Hz). Clinical evaluation included the registration of demographic data, disease duration, current treatment undergone0, joint swelling and tenderness. US study included the assessment of both inflammatory (joint effusion, synovial hypertrophy, local pathologic vascularisation at PD, big-toe bursitis) and structural (osteophytes, MTP joints subluxation) abnormalities. Results. One hundred patients were studied. At midfoot level, clinical examination demonstrated signs suggestive for joint inflammation (tenderness and/or swelling) in at least one joint in 43/200 feet (21.5%) of 23 patients; US showed inflammatory abnormalities in 87/200 feet (435%) of 63 patients and structural lesions in 100/200 feet (50%) of 70 patients. At forefoot level, clinical examination found inflammatory signs in at least one joint in 128 feet (64%) of 64 patients; US showed inflammatory abnormalities in at least one joint in 176 feet (88%) of 88 patients and structural lesions in 189 feet (86%) of 86 patients. Conclusions. US is a useful imaging tool for analysing both inflammatory and structural damage lesions at foot joints level in OA. In addition, it demonstrated to be more sensitive than clinical examination in the detection of inflammatory abnormalities.