Novak Djokovic's worst fears materialised as a knee injury forced him out of the French Open on Tuesday, while women's reigning champion Iga Swiatek surged into the semi-finals with another ruthless display.

Carlos Alcaraz served a convincing reminder of his Roland Garros title credentials after Djokovic's pull-out ensured there will be a new name on the men's trophy.

World number one and 24-time Grand Slam winner Djokovic withdrew ahead of his quarter-final against Casper Ruud after a scan revealed a torn medial meniscus in his right knee.

The 37-year-old Djokovic had blamed the "slippery" Roland Garros courts for aggravating the problem during his last-16 win on Monday.

"I am really sad to announce that I have to withdraw from Roland Garros," Djokovic wrote on social media.

"My team and I had to make a tough decision after careful consideration and consultation."

Ruud, who lost to Djokovic in last year's final, will receive a walkover and play Alexander Zverev or Alex de Minaur in the semi-finals on Friday.

Djokovic's injury-enforced exit from the tournament also means that Jannik Sinner will become Italy's first number one in the sport next week.

For the first time since 2004, the men's final in Paris will not feature Djokovic, Rafael Nadal or Roger Federer.

Second seed Sinner reached his first Roland Garros semi-final shortly after the news of Djokovic's withdrawal, beating Bulgaria's Grigor Dimitrov 6-2, 6-4, 7-6 (7/3).

"It's every player's dream to become number one in the world. On the other hand, seeing Novak retiring (from the tournament) is disappointing, so I wish him a speedy recovery," said Sinner.

The Australian Open champion goes through to a blockbuster clash with Alcaraz, a 6-3, 7-6 (7/3), 6-4 winner over Stefanos Tsitsipas in a repeat of last year's quarter-final.

Alcaraz is looking increasingly assured in Paris after an injury-hit preparation, and has now won all six encounters with Tsitsipas.

The 21-year-old Spaniard is seeking to become the youngest man to win Grand Slams on all three surfaces by adding to his Wimbledon title from a year ago and the 2022 US Open crown.

"It's going to be a really difficult challenge for me, but I'm ready to take that challenge," Alcaraz said of facing Sinner.

"It's the match everybody wants to watch... Let's see who's going to win."

The pair have split eight previous matches, with Alcaraz winning a five-set US Open quarter-final classic en route to the title two years ago in their most recent duel at a major.

Relentless Swiatek

Earlier in the day, Swiatek thrashed Wimbledon champion Marketa Vondrousova 6-0, 6-2 to set up a last-four showdown with American third seed Coco Gauff, the player she beat in the 2022 Roland Garros final.

World number one Swiatek improved her career record in Paris to 33-2 and is on course to become the first woman to lift the Coupe Suzanne Lenglen three years in a row since Justine Henin in 2005-07.

After Swiatek's 40-minute rout of Anastasia Potapova in the last 16, the only consolation for Vondrousova was her snapping the Pole's incredible run of 20 consecutive games won early in the second set.

"Honestly I think everything worked," said the 23-year-old Swiatek. "I felt like I was in the zone today."

Since saving a match point against Naomi Osaka in round two, Swiatek has looked every bit the tournament favourite and goes into her semi-final with Gauff having won 10 of their 11 meetings, all in straight sets.

US Open champion Gauff has come up short against Swiatek in four attempts on clay and was beaten by the top seed on her way to the title in Rome last month.

"You don't want to change your routines. Not to put too much baggage on your shoulders, just treat it like any other match and not something huge," said Swiatek.

Gauff passed her toughest test of the fortnight as she fought back from a set down to beat three-time Grand Slam finalist Ons Jabeur 4-6, 6-2, 6-3.

The 20-year-old Gauff is set for a third straight Grand Slam semi-final, after also making the last four at the Australian Open.

"Everybody knows I want to go all the way," said Gauff, who must try to end Swiatek's 19-match French Open winning run.

"I have nothing to lose. All the pressure is on her."