When to Use
- Replying to a friend who said something completely illogical.
- Commenting on a post that demonstrates poor decision-making.
- Used to jokingly insult a rival's lack of common sense during an argument.

A medical-style illustration shows a human brain replacing the kneecap in a leg, suggesting a metaphorical link between knee and intellect.
This meme is used to mock someone's lack of intelligence, implying their brain is located in their knee rather than their head.