Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius

Articulation of the radius to the humerus

That is how the ulna is articulated with the humerus; but where the radius is joined to the humerus, it is quite thin, and from a long, thin neck (M in figs. 3, 4, 9) [collum radii] it spreads into a wide, rounded capitulum (N in the same figs.) which forms, in the area facing the humerus, a circular depression (O in fig. 9) [fovea articularis] that is not very deep, which the head of the humerus 34 (P in fig. 1, ch. 23) [capitulum humeri] enters. Upon this head the radius pronates and supinates, 35 and does nothing to limit flexion of the elbow and extension of the joint of the radius with the humerus; 36 indeed, the depression of the radius also flexes and extends on the head of the humerus. The length of the head of the humerus particularly helps such motion, as does its broad surface coated with cartilage, which never leaves the depression in the radius during motions of the forearm. Nature’s artifice is not to be neglected or overlooked: she so adapted the joint of the humerus with the radius that the radius and ulna can be flexed and extended, and at the same time the radius can be supinated and pronated while the ulna is not moving on the humerus.



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius