'Knees' in the Bible

And it was so, that when Solomon had ended praying all this prayer and supplication to Jehovah, he arose from before the altar of Jehovah, from kneeling on his knees with his hands spread forth to the heavens,

And Ahab went up to eat and to drink. And Elijah went up to the top of Carmel; and he bowed down on the earth, and put his face between his knees.

Yet I have left myself seven thousand in Israel, all the knees that have not bowed unto Baal, and every mouth that hath not kissed him.