'Knees' in the Bible

It was so, that when Solomon had made an end of praying all this prayer and supplication to Yahweh, he arose from before the altar of Yahweh, from kneeling on his knees with his hands spread forth toward heaven.

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

Yet will I leave seven thousand in Israel, all the knees which have not bowed to Baal, and every mouth which has not kissed him."