Posterior border of radius

The posterior border (dorsal border) begins above at the back of the neck, and ends below at the posterior part of the base of the styloid process; it separates the posterior from the lateral surface. It is indistinct above and below, but well-marked in the middle third of the bon

The posterior border is distinct from the interosseous (medial) border that is the sharp margin on the medial side of the shaft that gives attachment to the interosseous membrane and separates the anterior and posterior surfaces; it extends from just below the radial tuberosity to the ulnar (sigmoid) notch. The posterior border, by contrast, delimits the boundary between the posterior and lateral surfaces.