Pope John Paul II (search) turned 83 Sunday and was joined by thousands of his fellow Poles at a canonization Mass in a packed St. Peter's Square.
He received birthday greetings in Latin from one of his closest advisers, Cardinal Joseph Ratzinger, and loud applause from the crowd of tens of thousands when he arrived for the service.
John Paul sat in hydraulic chair that allows him to celebrate Mass while seated. He suffers from crippling knee and hip ailments.
A top Vatican official acknowledged Saturday what many observers have long suspected -- that John Paul also suffers from Parkinson's disease (search).
The Vatican (search) has never officially acknowledged the source of the pope's trembling hands and slurred speech, typical symptoms of the degenerative neurological disorder.
Cardinal Giovanni Battista Re, head of the Congregation of Bishops, said in a newspaper interview that prayer allows the pope to cope with the ailment.
Two Poles and two Italians -- all founders of religious orders -- were being elevated to sainthood. John Paul has already proclaimed 469 saints, making him the greatest saint-maker in the Church's history.
The birthday celebration is one of a series of milestones for John Paul, who recently became the fourth longest-serving pope in history. A visit to Croatia next month will be his 100th foreign tour, while the Church is preparing to mark his 25th anniversary as pontiff on Oct. 16.