Figure 1.

Codman’s paradox. A man places both arms along the body with the palms faced anteriorly. He elevates one arm 90 degrees forward without rotation. The palm faces superiorly. Following that, he abducts the same arm at 90 degrees horizontally. The palm still faces superiorly. Finally, the arm is adduced 90 degrees downward. Now, the direction of the palm is altered from the first direction.