Pope Celebrates Christmas Mass

Dec. 24: Pope Benedict XVI kneels in prayer during Christmas Mass in St. Peter's Basilica at the Vatican. (AP)

Dec. 24: Pope Benedict XVI is assisted as he arrives for Christmas Mass at St. peter's Basilica.    (AP)

Dec. 24: Pope Benedict XVI greets the faithful as he arrives for Christmas Mass in St. Peter's Basilica.  (AP)

Dec. 24: In this image made from the Vatican television, Vatican security rush to add Pope Benedict XVI, not seen, after a woman knocked him down.  (AP)

Dec. 24: A general view of St. Peter's Basilica. (AP)