If I was standing, my knees would be knocking together.

When a tree really looks like a man our knees knock under us.

Mallory didn't think she'd be able to walk without her knees knocking together again.

The man's knee knocked against the wall like a nail going into a coffin.

All the color left his face, and his knees knocked.

I guess your knees really can knock if you're frightened enough.

She didn't think she was going to be able to stand, her knees were knocking so hard.

Based on all I'd heard, when I was standing next to him, my knees were knocking.

For the moment, Harry's knees knocked together as the tremor reached them.

His knees weren't knocking together, but they weren't far from it.