I need some forearm bone motion pictures
Here is a basic image. Palm up is called supination and is the resting (anatomical) position. The radius and ulna sit parallel. When the forearm is in pronation, the radius crosses the ulna.

You can feel this yourself. Put your fingers on the ulna and move the palm into pronation and supination. You will not feel the ulna rotate. Only the radius pivots during this movement. The wrist is not involved in this movement.



The ulna is unable to rotate at all, because its olecranon process is locked into a groove on the distal end of the humerus. If you put you fingers on your bony "elbow" (olecranon process) and pronate/supinate your hand (without flexing/extending your elbow), you will not feel you ulna moving.