Ooops. Correction.

My friend Paul corrected me on one point about the elbow. I meant to say "ulnar-humeral joint" not the "radial-humeral joint." He further pointed out that the head of the radius is what allows for pronation and supination of the lower arm. That is true, but the entire process would be much harder were it not for the ball at the proximal—not distal—end of the humerus.