'Knees' in the Bible

Then the colour went from the king's face, and he was troubled by his thoughts; strength went from his body, and his knees were shaking.

And Daniel, on hearing that the writing had been signed, went into his house; (now he had windows in his room on the roof opening in the direction of Jerusalem;) and three times a day he went down on his knees in prayer and praise before his God, as he had done before.

Then a hand gave me a touch, awaking me, and putting me on my knees and my hands.