"Due to a torn medial meniscus in his right knee (discovered during an MRI scan performed today), Novak Djokovic... has been forced to withdraw from the Roland Garros tournament," organisers said in a statement.

World number one and 24-time Grand Slam champion Djokovic was due to play Ruud on Wednesday for a place in the last four. Djokovic defeated Ruud in last year's final at Roland Garros.

As a result Ruud will go on to face fourth seed Alexander Zverev or 11th seed Alex de Minaur in the semi-finals on Friday.

The 37-year-old Djokovic had cast doubt over his fitness following Monday's five-set win over Francisco Cerundolo, admitting he needed anti-inflammatory drugs to get through the match.

Djokovic blamed the "slippery" Philippe Chatrier court for the injury he sustained early in the second set of his 6-1, 5-7, 3-6, 7-5, 6-3 victory over Cerundolo.

"I don't know what will happen tomorrow or after tomorrow if I'll be able to step out on the court and play. You know, I hope so. Let's see what happens," Djokovic said after the match.

"For the last couple weeks I have had, I would say, slight discomfort, I would call it that way, in the right knee, but I haven't had an injury that would be concerning me at all.

"I was playing a few tournaments with it, and no issues until today."

Djokovic's withdrawal from the French Open means that Jannik Sinner will become Italy's first men's world number one next week.

The Serbian star arrived at the tournament with his status at the top under threat from Sinner, who was guaranteed to supplant Djokovic if the latter failed to reach the final in Paris.

Djokovic has spent a record 428 weeks at the top of the rankings.

His injury extends his worst start to a season since 2018, when he didn't win an event until claiming the Wimbledon title.

Adding to his problems, he was accidentally hit on the head by a metal water bottle in Rome last month before suffering stomach problems in Geneva.

Djokovic last pulled out of a Grand Slam during the 2019 US Open, when a shoulder problem forced him to quit against Stan Wawrinka in the last 16.