Some information on the traditions of the Ukrainian Catholic Chruch can be found here.
No Kneeling during Liturgy from Pascha to Pentecost: Starting at the Feast of Pascha, and continuing until Pentecost Sunday (even throughout the week), we do not kneel during the Divine Liturgy. Kneeling is a sign of penance and contrition - but the joy of Pascha is so much greater in this season that we stand in celebration instead.