Figure 1: Sonographic transverse views of the knee joint. (a) A characteristic sonographic appearance of crystal deposits (arrows) on the surface of the hyaline cartilage (*) in gout (”double contour” sign) is noted. (b) It discloses typical hyperechoic material consistent with calcium-containing crystal deposition (arrow heads) within the articular cartilage (*) in a patient with chondrocalcinosis