The radius is one of the two forearm bones, positioned laterally and shorter than the ulna, whose proximal head articulates with both the capitulum of the humerus and the radial notch of the ulna, an arrangement of two simultaneous articulations that enables elbow flexion together with pronation and supination (the rotation of the forearm bones relative to one another). Distally, the radius bears the ulnar notch (articulating with the head of the ulna), the radial styloid process, and a dorsal tubercle that functions as a pulley redirecting the line of pull of the thumb's extensor muscles, illustrating the general anatomical principle that specific bony landmarks (articular surfaces, processes, tubercles) determine the joint's available range of motion and the mechanical advantage of attached muscles.
The radius is one of the two forearm bones, positioned laterally and shorter than the ulna, whose proximal head articulates with both the capitulum of the humerus and the radial notch of the ulna, an…