In relation to the ulna, the radius is?

In relation to the ulna, the radius is?

• A. Lateral
• B. Medial
• C. Proximal
• D. Distal

Answer: (A)

The main idea is the left–right spatial relationship of the forearm bones in standard position. In anatomical position, the radius sits on the lateral (thumb) side of the forearm, while the ulna is on the medial (pinkie) side. So, relative to the ulna, the radius is lateral. Proximal and distal describe ends of the bones (closer to the elbow or wrist), not side-to-side position, and medial would place it on the inner side, which isn’t correct here. (Note: during pronation the radius crosses over the ulna, changing their relative positions, but in the usual reference position the radius is lateral to the ulna.)

The main idea is the left–right spatial relationship of the forearm bones in standard position. In anatomical position, the radius sits on the lateral (thumb) side of the forearm, while the ulna is on the medial (pinkie) side. So, relative to the ulna, the radius is lateral. Proximal and distal describe ends of the bones (closer to the elbow or wrist), not side-to-side position, and medial would place it on the inner side, which isn’t correct here. (Note: during pronation the radius crosses over the ulna, changing their relative positions, but in the usual reference position the radius is lateral to the ulna.)