Ultrasound and clinical features of hip involvement in patients with gout

To investigate the prevalence of the ultrasound findings indicative of monosodium urate crystal deposits at the hip joint in patients with gout and to explore the association between the ultrasound findings and the clinical and serological features.

Bilateral ultrasound assessment of the hip joint was carried out in 40 consecutive patients with gout, diagnosed according to the latest Gout American College of Rheumatology/European League Against Rheumatism classification criteria, and 25 disease controls. Ultrasound evidence of crystal deposits was obtained using the Outcome Measures in Rheumatology definitions: hip intra-articular aggregates and/or tophi, and "double contour" sign over the hyaline cartilage of the femoral head.

The ultrasound examination revealed crystal deposits in at least one hip in 17 out of 40 patients (42.5%) with gout, and in 2 out of 25 disease controls (8.0%) (P = 0.0029). Aggregates, tophi, and "double contour" sign were found in at least one hip in 13 (32.5%), 6 (15.0%) and 6 (15.0%) out of 40 patients with gout, respectively. A moderate association between disease duration (P = 0.004, Rpb = 0.442), number of gouty "attacks" in the previous year (P = 0.029, Rpb = 0.346), presence of subcutaneous tophi (P = 0.037, V = 0.330) and ultrasound crystal deposits was found.

Our results indicate that detecting monosodium urate crystals by ultrasound is common at hip joint in patients with gout.