To genuflect means, literally, “to bend the knee.” In the ancient world the knee symbolized the strength of a man. If a man is struck in the knee, he stumbles and falls; his strength is taken from him. When we genuflect before the Lord, our strength is not taken from us; rather, we willingly bend our strength to the Lord and place ourselves humbly in his service. When we bend our knee to the Lord of heaven and earth we should hear the words of the Psalmist ever in our hearts, “Lord, I am your servant,” remembering that before the Lord every knee must bend (Psalm 116:16; cf. Philippians 2:10).
—from Bishop Thomas Paprocki’s pastoral letter Ars celebrandi et adorandi, On the Art of Celebrating the Eucharistic Liturgy Properl and Adoring the Lord in the Eucharist Devoutly