The radius is structured as one piece with two ends, the radial head, radial styloid, ulnar styloid, and the body of the radius. The upper end forms the flattened, rounded head of the radius, and the head is surmounted by the concave radial head recess, which is articulated with the humeral tuberosity. The circumference of the radial head has a circumferential articular surface that articulates with the radial notch of the ulna. The radial neck is smooth and thin below the radial head, and there is a large rough elevation called the radial trochlea on the inner lower part of the neck, which is the stop of the biceps muscle. The medial margin of the body is sharp, also known as the interosseous ridge, opposite the interosseous ridge of the ulna. The rough surface at the midpoint of the lateral surface is the prehensile round muscle rudiment. The lower end is particularly inflated and nearly cuboidal. Its distal surface is smooth and concave and is the carpal articular surface, articulating with the proximal carpal bones. The medial side has an ulnar notch and is associated with the ulnar head. The lateral surface protrudes downward and is called the radial tuberosity.