According to the US Tennis Association (USTA), Vondrousova is the first woman to give her opponent a walkover — the term for when a tennis player withdraws from a match before it begins — at Flushing Meadows in the quarters or later since 1988, when Steffi Graf advanced to the final when Chris Evert did not play their semi.
"I tried my best to take the court today, but during the warm-up, I felt again my knee, and after consultation with the tournament doctor decided not to risk aggravating the injury," Vondrousova, a 26-year-old left-hander from the Czech Republic, said in a statement released by the USTA.
"I appreciate all the support this tournament and apologise to the fans who were looking forward to the match."
Sabalenka will meet No.4 seed Jessica Pegula in the last four in a rematch of last year's championship match, which the Belarusian won in straight sets.
Earlier on Tuesday, Pegula showed again the benefits of home, defeating Barbora Krejcikova 6-3 6-3 to reach a grand slam semi-finals for the second time in her career, both in New York.
The American failed to advance to the semis in her first 23 main-draw appearances at a major before reaching the 2024 decider.
She has since been eliminated in the fourth round at the Australian Open, third round at the French and first round at Wimbledon.
Being back on hard courts at the US Open has been a recipe for success.
"I think I've been playing some really good tennis," Pegula said.
"I've just been playing very solid. I've been having very good quick starts, so I really wanted to do that today, especially against someone like (Krejcikova) who's very dangerous.
"It's crazy to look now and think that I'm really comfortable coming out here playing on big courts in big matches on the best court in the world with the craziest crowd against the best players."
Pegula was not perfect, but she played well enough to stay in control throughout and broke for a fifth time to end the match in under 90 minutes — on her first match point attempt.
She had been 0-6 in major quarter-finals until upsetting Iga Swiatek in that round at Flushing Meadows a year ago.
Now the 31-year-old is the first woman to make the final four at the US Open in consecutive years without losing a set since 23-time major champion Serena Williams did it every year from 2011 to 2014.
"I've been able to kind of go into those matches and really take care of business," Pegula said.
