Kneeling has always been a gesture of reverence; but the practice of genuflecting – touching the right knee briefly to the ground – is comparatively recent. “It appears to have been introduced and gradually to have spread in the West during the later Middle Ages,” says the Catholic Encyclopedia, “and scarcely to have been generally looked upon as obligatory before the end of the 15th century.” Even today, Eastern Catholics are more likely to bow than genuflect.
With some exceptions, genuflection is basically how we should show our love for Jesus in the Blessed Sacrament. Priests genuflect three times in the Mass – after the elevation of the Body of Christ, after the elevation of the Precious Blood, and before Holy Communion. Everyone, meanwhile, should genuflect when crossing in front of the tabernacle; if the Blessed Sacrament is reserved in the church, one genuflects when entering and leaving the church.
We also genuflect during the words “and the Word was made flesh” when saying the Angelus, and during the Last Gospel in the Traditional Latin Mass (there are a handful of other occasions in the traditional liturgical year). From Good Friday to the Easter Vigil, the custom is to genuflect to the Holy Cross.
When the Blessed Sacrament is exposed, it’s customary to genuflect on both knees and bow.