Serena Williams withdrew from the Wimbledon doubles match where she was scheduled to play with her sister Venus, citing a knee injury.

“I’m heartbroken to have to withdraw from doubles. Coming back to compete again has been a gift, and the opportunity to play alongside @venuswilliams once more meant the world to me,” she wrote on Instagram Saturday.

“I did everything I could to be ready, but unfortunately my knee just isn’t ready to compete.” 

The 44-year-old Williams recently returned to competition after nearly four years away from professional tennis.

Williams lost her singles match at Wimbledon to 20-year-old Maya Joint in the first round after accepting a wild card invitation. She had accepted an earlier wild card invitation for the doubles competition with her older sister Venus.

Venus, who has still been competing sporadically, turned 46 in June. 

Serena won 14 Grand Slams in doubles, all with Venus, and six of them at Wimbledon. The sisters last played a doubles match at the 2022 U.S. Open.  They lost their opening match against the Czech pair of Lucie Hradecka and Linda Noskova. That was the first time they’d played doubles together in 4-1/2 years.

Williams also won 23 Grand Slam titles in singles, including seven at Wimbledon.