During full forearm supination, what happens to the radial head?

• A. Moves Anteriorly
• B. Moves Posteriorly
• C. Stays in Place
• D. Rotates Medially

Answer: (A)

When the forearm supinates, the radius rotates around the ulna at the proximal radioulnar joint, and the radial head shifts forward within the annular ligament to accommodate that rotation. This anterior translation happens to allow the radius to arc into the supinated position while the head remains constrained by the ulna and the ligament hoop. So, in full supination, the radial head moves anteriorly.

It doesn’t stay fixed, it isn’t translating posteriorly in this motion, and the main directional change of the proximal end is a forward glide rather than a medial rotation of the head itself.