Double contour (DC) sign in an ultrasonography (US) scan of the knee.Longitudinal US shows a DC sign (arrows) in a patient with gouty arthritis of the knee, with a hyperechoic band over the articular cartilage (hypoechoic) of the medial condyle. Note: The DC sign has the same thickness as the cortical bone, and is continuous apart from a small defect (arrowhead).