PARIS -- Novak Djokovic has been forced to withdraw from his French Open quarterfinal against Casper Ruud due to the right knee injury he sustained in his fourth-round win Monday.
The move ends his title defense and means he will relinquish the No. 1 ranking.
Djokovic underwent an MRI scan and further medical tests on his knee Tuesday. A statement from Roland Garros said he suffered a "torn medial meniscus" of his right knee.
Djokovic said Monday he was hurt in the second set of his eventual five-set win over Francisco Cerundolo. He was hopeful of competing in his quarterfinal Wednesday.
In a statement, Djokovic said that he played with his heart and gave it his all Monday before getting injured.
"I wish the best of luck to the players competing this week and sincerely thank the incredible fans for all of the love and continued support," he said.
The 24-time Grand Slam champion said he had slight discomfort in his right knee coming into the tournament but had no further issues until his mammoth fourth-round match Monday. His third-round match finished at 3:07 a.m. on Sunday and he said that late finish "didn't help the sleeping, the biorhythm, and recovery."
After taking the first set against Cerundolo, Djokovic said a slip in the third game of the second set "affected the knee." He requested a medical timeout and had further physio treatment on it during the match.
Djokovic was visibly frustrated with how slippery he was finding the surface on Court Philippe-Chatrier and asked for it to be swept more frequently. But the request was rejected.
"I started feeling the pain and asked for the physio treatment and the medical timeout and tried to take care of it. It did disrupt me definitely in play," Djokovic said Monday evening. "For two sets, two sets and a half, I didn't want to stay in the rally too long. Every time he would make sudden drop shots or change directions, I would not be feeling comfortable to do the running.
"At one point I didn't know, to be honest, whether I should continue or not with what's happening. I got the medications, and then after the third set was done, I asked for more medications, and I got them.
"That was the maximum dose that kicked in, as I heard now from doctor after 30 to 45 minutes, which was just about the time kind of end of the fourth when things started to really improve for me. I started to feel less limitations in my movement."
Down two sets to one and a break in the fourth set, Djokovic rallied to win the match, but he was left concerned with what long-term damage he had done to his knee in the process.
Djokovic, 37, now sets his sights on Wimbledon, which starts on July 1. Then there are the Olympic Games starting July 27. Djokovic's withdrawal means Ruud has booked his spot in the semifinals. He will play the winner of Alexander Zverev and Alex de Minaur's Wednesday quarterfinal.