His sudden smile made her go weak at the knees.

他突然笑了笑，使得她两膝发软。

《牛津词典》

Fine, really. A bit weak at the knees but that will soon pa ss.

很好，真的。两腿有点发软，但很快就会好的。

youdao

Rudolph, the Adonis of the silent films, had one great quality - to make women feel weak at the knees.

鲁道夫，这部无声电影中的美男子，有一个绝妙的本事——使女人感到两腿发软。

youdao

For Mr Bush, who has openly campaigned to defend the interests of the oil industry, to go suddenly weak at the knees about high oil prices is bizarre.

ECONOMIST: Pump fiction | The

Feeling suddenly weak in the knees, I sank back on the hard train seat and glanced again at the gloomy landscape lumbering past the window.

NPR: Excerpt: The Sherwood Ring

One might expect that at the ripe old age of 100 the company would be creaking along with brittle bones, weak knees, a bad heart, and finding it hard to get up in the morning.

FORBES: Happy 100th Birthday IBM!