It's out of fashion now. I can't really remember when it stopped but it must have been at least forty years ago.
Psalm 95:6. "Oh come, let us worship and bow down; Let us kneel before the LORD our Maker."
Daniel 6:10. "Now when Daniel knew that the writing was signed, he went home. And in his upper room, with his windows open toward Jerusalem, he knelt down on his knees three times that day, and prayed and gave thanks before his God, as was his custom since early days."
Philippians 2:10. "..that at the name of Jesus every knee should bow..."
Luke 5:8. "When Simon Peter saw it, he fell down at Jesus’ knees, saying, “Depart from me, for I am a sinful man, O Lord!” "
Luke 22:41. "And He was withdrawn from them about a stone’s throw, and He knelt down and prayed..."
Ezra 9:5. "...I fell on my knees and spread out my hands to the LORD my God."
Acts 9:40. "But Peter put them all out, and knelt down and prayed."
Acts 20:36. "And when he had said these things, he knelt down and prayed with them all."
Mark 10:17. "Now as He was going out on the road, one came running, knelt before Him, and asked Him, “Good Teacher, what shall I do that I may inherit eternal life?” "
Matt. 17:14. "And when they had come to the multitude, a man came to Him, kneeling down to Him and saying..."
Eph. 3:14. "For this reason I bow my knees to the Father of our Lord Jesus Christ..."
Acts 21:5. "And we knelt down on the shore and prayed."
1 Cor. 14:25. "...and so, falling down on his face, he will worship God and report that God is truly among you."
We have lost something if we have given up praying on our knees before Him. The same loss of reverence, honor and respect that has invaded our culture has invaded our Christian lives as well, I fear.
Have you ever felt the need to prostrate yourself before Him? The dictionary definition is "to cast (oneself) face down on the ground in humility, submission, or adoration."
To the best of my recollection, it seems that the only time the Bible refers to standing while praying was when it was speaking about the haughty Pharisees. Our prayer posture is usually a reflection of the posture of our hearts.