Handbook of Liturgical Practice of the Russian Church Abroad
Kneeling (i.e. standing on one’s knees) is not a traditional posture of prayer for the Divine Services in Orthodoxy. The only occasion on which we kneel in the temple, rather than prostrate ourselves, is during the ‘Kneeling prayers’ on the Vespers of Holy Pentecost.
At all other times we are either standing, or we make a full prostration to the ground.