Neymar underwent surgery on Thursday at a hospital in his native Brazil to repair a torn anterior cruciate ligament and meniscus damage suffered during a national team match last month.
"The operation was a success. We're very satisfied with the result," said Rodrigo Lasmar, the Brazilian team doctor who performed the surgery.
"He had a reconstruction of the anterior cruciate ligament and the two meniscus injuries have been repaired."
Neymar is expected to remain at Mater Dei hospital in the southeastern city of Belo Horizonte for another 24 to 48 hours while he recovers, the doctor added.
Lasmar previously operated on Neymar for a foot fracture in 2018.
The 31-year-old was stretchered off in tears during Brazil's 2-0 loss to Uruguay in a World Cup qualifying match on October 17, after colliding with opposing midfielder Nicolas de la Cruz.
Exams found the star striker had torn his left anterior cruciate ligament, one of the most serious knee injuries in football.
The injury is expected to sideline him for several months, including for Brazil's upcoming 2026 World Cup qualifiers this month against Colombia and arch rivals Argentina.
It is the latest in a string of injuries for Neymar, who underwent surgery in March for an ankle problem that sidelined him for six months.
Fitness problems overshadowed much of his six seasons at Paris Saint-Germain, who signed him for a world-record €222 million in 2017.
He signed for Al Hilal for a reported $95 million in August 2023.
Despite his injury battles, Neymar etched his name in the record books in September when he surpassed the legendary Pele to become Brazil's all-time leading goal scorer, with 79.