Abnormal forearm morphology Ulnar positive variance 2025-11-19T09:34:39Z A phenomenon whereby the distal ulna articular surface is more distal than the distal radius articular surface. The triangular fibrocartilage complex (TFCC) is a well-defined anatomical entity of the wrist joint known as the primary stabilizing structure of the distal radioulnar joint (DRUJ). The TFCC provides considerable DRUJ stability. The instability of DRUJ caused by the foveal tear of the TFCC also results in an abnormal anatomic relationship between the radius and ulna. When the foveal attachment of the TFCC is disrupted, the ulnar head is free to sublux dorsally relative to the sigmoid notch of the radius, which is aggravated under the stress of pronation. This change in the anatomic relationship between the radius and ulna can be easily observed on plain radiographs.