Which bone forms the outer part of the forearm?

The radius is the bone in the forearm that forms its outer part, particularly in the anatomical position when the palms face forward. It is situated on the lateral side, which is the side of the thumb. The radius not only contributes to the structure and stability of the forearm but also plays a key role in the movement of the wrist and elbow through its articulation with the humerus at the elbow and with the carpal bones of the wrist.

In contrast, the ulna is located on the medial side of the forearm, opposite the radius, and its primary functions are to provide structural support and to form a joint with the humerus and wrist. The humerus is the upper arm bone and does not form part of the forearm itself, while the clavicle is the collarbone, which connects the arm to the body but is not involved in forearm structure or function. This distinction in location and function helps clarify why the radius is considered the outer bone of the forearm in contrast to the other bones mentioned.