Milan - Italy hooker Leonardo Ghiraldini suffered ruptured cruciate knee ligaments in the team's final Six Nations game, the Italian rugby federation (FIR) confirmed on Monday.
Toulouse hooker Ghiraldini, 34, was carried off to thundering applause for his final home game in Rome after 104 caps in a 25-14 defeat to France on Saturday.
"Tests showed the rupture of the cruciate ligament of the right knee, involving the medial ligament and the meniscus," FIR said in a statement.
"In the next few days the athlete will evaluate, together with the medical staff of the national team and the club he belongs to, the methods and timing of the operation and the functional recovery programme."
His absence will also be a blow for Top 14 leaders Toulouse, as well as Italy as they prepare for the World Cup in Japan from September 20 to November 2.
Ruptured knee ligaments typically take a minimum of six months to heal, making him doubtful for the global showpiece.
"I want to thank (coach) Conor (O'Shea), (captain) Sergio (Parisse) and all the team-mates of the national team and the club for being close to me immediately after the injury and all the people who continue to support me with their enormous affection," said Ghiraldini.
"For me a new challenge has already begun and I will face it with all the determination possible to reach the next goal, to be able to return to the highest levels and be selected for the upcoming Rugby World Cup."
Italy lost their 22nd consecutive game in the Six Nations to earn a fourth consecutive wooden spoon.