For Catholics, kneeling is one of the distinctive physical gestures of prayer during the celebration of Mass. Even, for many centuries the lay faithful of the Roman Rite would kneel for almost through out the duration of Mass.
As it’s true that standing during prayer used to be a common posture of the early Christians (and is still maintained currently by many Eastern Christians during the Divine Liturgy), kneeling was also part of the early Christian tradition.
Cardinal Joseph Ratzinger explains that, kneeling was something highly disfavored by both Greek and Roman culture.
Ratzinger writes in his book called the Spirit of the Liturgy, “If we look at history, we can see that the Greeks and Romans rejected kneeling and kneeling was unworthy of a free man, unsuitable for the culture of Greece, something the barbarians went in for. Though, Plutarch and Theophrastus regarded kneeling as an expression of superstition and Aristotle called it a barbaric form of behavior.”
Ratzinger also claimed that, “Kneeling does not in any way come from any culture rather it comes from the Bible and its knowledge of God.” Saint Luke, particularly in his whole work (both in the Gospel and the Acts of the Apostles) and in a special way the theologian of a kneeling prayer, tells us that even Jesus prayed on His knees. The prayer that Jesus prayed when he was about to enter into his passion is a typical example for us. As thus, Catholics kneel during prayers and during Holy Mass because Jesus kneeled during prayer.
In addition, kneeling is typically seen in the Gospels as a means to express supplication and adoration. Most often kneeling is preceded by an act of faith in the New Testament.
As many as the healing narratives that came up in the Bible, the person is always presented kneeling in supplication, asking to be healed.
In that case, the Roman Rite instructs the faithful to kneel during Mass and specifically when Jesus is made present on the altar.
In accordance with the General Instruction of the Roman Missal , “In the Dioceses of the United States of America, the faithful should kneel starting after the singing or recitation of the Sanctus (Holy, Holy, Holy) until after the Amen of the Eucharistic Prayer.”
Kneeling is meant to express a spiritual attitude of adoration before the triune God, who is truly and substantially present in the Holy Eucharist. It is also an act of humility, recognizing our own littleness before the Creator of the world. And it prepares our hearts to receive God within our souls, bringing down our pride with a physical reminder of what our soul should be like spiritually.
However, kneeling in the context of the Roman liturgy is directly tied to the presence of Jesus in the Eucharist.
As it is not officially part of the Rite, it is a common custom in most churches to maintain a kneeling posture until the consecrated hosts are placed back within the tabernacle.
Kneeling during Mass is an ancient style, one that expresses an inner spiritual truth that is connected to the Real Presence of Jesus on the altar.