Meaning of "her knees have knocked each other senseless"?

Hello everyone. I am reading a novel, and I came across this expression. Could you please let me know its meaning?

“What do you think?”

“Of these books?”

“No, of her.”

I looked at the blond woman she was indicating. Her name was Beryl, she said.

“I don’t know. Nice, I suppose,” I said. I could tell Clara would have preferred a devastating bashing on the spot. But I also wanted her to know that I was merely pretending to be naive and was just holding out before delivering my own demolition job. She didn’t give me time.

“Skin’s as white as aspirin, cankles the size of papayas, and her knees have knocked each other senseless—don’t you notice anything?” she said. “She’s walking on her hindquarters. Look.”

- André Aciman, Eight White Nights, First Night

This is a novel published in the United States of America in 2010. This novel is narrated by the nameless male protagonist who meets Clara at a Christmas party in Manhattan. Now Clara is pointing at Beryl and talking about her gait.

In this part, I wonder what the underlined expression means.

Would that perhaps mean that her knees hit against each other so that her knees fainted...? (But this is just my wild guess. )I wonder whether it is just another way to say that her knees are very close to each other... Thank you very much for your help.