Depending on the tradition from which you came into Orthodoxy, you might have been much more accustomed to kneeling than we typically do. The bending of our knees is sometimes called the “lesser penance” (understandable for those of us with creaky, old knees), and is part of why some choose to kneel to receive absolution following Confession. Handy perhaps that we discuss this on this particular Sunday when we also celebrate the Kneeling Vespers of Pentecost. This is basically just another Vespers service, but a special one to which we add three rather long sets of noetical prayers, written by St. Basil the Great, during which we traditionally make a full prostration (if you’re physically able).
Incidentally, this is the first time since Pascha that prostrations are allowed to make full prostrations according to the canons. Here at St. Andrew’s it has been our practice to conduct this service immediately following the Divine Liturgy prior to trapeza.