Exam category: Procedures → Extremity
Why it matters: The forearm and elbow are where one mechanical fact — the radius pivoting over the ulna — explains almost everything the registry asks. It is why the forearm is supinated, why external rotation separates the two bones at the elbow and internal rotation superimposes them, and why the Coyle method exists. On top of that sits the elbow's fat-pad sign, which is genuinely useful clinically and comes with a flexion condition students routinely forget.
Hand and wrist covered the distal end of the limb. The theme changes here — instead of getting a small bone closest to the receptor, the whole game is controlling rotation, because the radius and ulna cross over each other whenever the hand turns. Get the rotation right and both bones lie side by side; get it wrong and they superimpose. The limb finishes in Shoulder girdle.
Routine: AP, lateral.
The forearm is not radiographed pronated. Pronating the hand pivots the radius so it crosses over the ulna in the upper forearm, superimposing the two bones. Radiographing AP with the hand supinated (palm up, anatomic position) keeps the radius and ulna parallel and side by side, which is the whole point of the projection.
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A forearm is radiographed AP with the hand pronated instead of supinated. What happens to the two forearm bones?
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