PARIS — Novak Djokovic withdrew from the French Open with an injured knee on Tuesday, ending his title defense and meaning he will relinquish the No. 1 ranking.

The tournament announced the news, saying Djokovic has a torn medial meniscus in his right knee. The extent of the injury was found during an MRI exam a day after Djokovic was hurt during a fourth-round victory against No. 23 Francisco Cerundolo that lasted five sets spread across more than 4 1/2 hours.

The 24-time Grand Slam champion was supposed to face No. 7 Casper Ruud, the runner-up each of the past two years at Roland Garros, in the quarterfinals on Wednesday. Instead, Ruud gets a walkover into the semifinals, where he will face No. 4 Alexander Zverev or No. 11 Alex de Minaur.

With Djokovic, the owner of three French Open titles, gone from the bracket, and Rafael Nadal — owner of a record 14 — eliminated in the first round, someone will be holding the French Open men’s trophy for the first time on Sunday.

The group of remaining contenders includes current No. 2 Jannik Sinner, a 22-year-old Italian who defeated No. 10 Grigor Dimitrov 6-2, 6-4, 7-6 (3) on Tuesday to reach the semifinals and now is assured of replacing Djokovic atop the ATP rankings next week.

Sinner won the Australian Open in January and is the first man from his country to reach No. 1.

“Seeing Novak (injured) is, for everyone, disappointing,” Sinner said, “so I wish him a speedy recovery.”

Amid a season in which Djokovic is only 18-6 and has not reached a final at any tournament, let alone won one, he needed to get back to the title match at the French Open to continue to add to his record for most weeks at No. 1.

For years and years, Djokovic, Nadal and Roger Federer ruled men’s tennis as the so-called Big Three, accumulating a total of 66 major championships among them. But Federer, now 42, is retired, and Nadal, who turned 38 on Monday, is trying to figure out how much longer he can compete after missing most of the past 1 1/2 seasons with injuries.

No one knows yet how long Djokovic, 37, will be sidelined or what, if any, effect this might have on his future.

Wimbledon, where has won seven titles, starts July 1, and the tennis competition at the Paris Olympics starts at Roland Garros on July 27.

Djokovic’s knee had been bothering him for a couple of weeks before he arrived in Paris for the French Open — something he kept to himself until after the win against Cerundolo. Early in the second set Monday, Djokovic tweaked his knee and took a medical timeout. A trainer worked on the joint then and during subsequent changeovers, and Djokovic took what he said a tournament doctor told him was the maximum dose of pills allowed to dull the pain and reduce any inflammation.

“I don’t know what will happen tomorrow — or after tomorrow, if I’ll be able to step out on the court and play,” Djokovic said Monday evening. “You know, I hope so. Let’s see what happens.”

Djokovic trailed by two sets to one, and was down a break at 4-2 in the fourth, against Cerundolo before raising his level of play once the medication kicked in.

“I was,” Djokovic said afterward, “maybe three or four points away from losing this match.”

Yes, he stuck it out, and, yes, he came back to win — it was his 370th victory in Grand Slam play, breaking a tie with Federer for the most in tennis history — but it was costly. And Djokovic said Monday he thought it could have been prevented if the clay inside Court Philippe Chatrier had been cared for better.

Both in that match — and during his 4 1/2-hour victory in the third round, which ended at after 3 a.m. Sunday — Djokovic tried to get the chair umpires to have the court swept more frequently to improve traction.

“I mean, today I injured myself. Yes, I survived. I won the match. Great. But will I be able to play next one?” he said, tapping his palms on a table for emphasis. “I don’t know. I don’t know the severity of the injury. But could have this injury be prevented? Possibly, if there was just a little bit more of a frequent care of the court during the set.”