I went to the doctor because my elbow was falling out of my arm.

This doctor joke plays on the delightful absurdity of taking an idiom literally. The setup paints a rather grotesque picture of a limb detaching itself, immediately grabbing our attention with its sheer impossibility. We're imagining a truly dire medical crisis, perhaps even a scene from a cartoon.

The punchline then cleverly pulls the rug out from under our literal interpretation, revealing that "falling out" was merely a humorous exaggeration for the common experience of overstretching. It’s the kind of discomfort many of us have felt after an enthusiastic yoga session or a vigorous warm-up. The doctor's advice, in this context, becomes perfectly sensible, contrasting sharply with the initial dramatic image. It’s a classic example of misdirection (Review), where the humor springs from the unexpected, yet perfectly logical, reinterpretation of a dramatic phrase.