Brooks Koepka tied for the most wins on the PGA Tour in 2019 despite having a knee injury that required stem cell surgery during the offseason.

Per the Associated Press (h/t ESPN.com), the four-time major champion revealed he had treatment on his left patella one day after the Tour Championship ended on Aug. 25. 

Koepka noted his knee started giving him problems in March and he needed three to four weeks of rehabilitation after having the procedure. 

The 29-year-old won the PGA Championship and PGA of America Player of the Year award for the second consecutive year. His three tournament victories tied Rory McIlroy for most on the circuit, and he finished in the top four in all four major championships. 

In between those performances, Koepka did have some struggles as the season wore on. The Florida native finished 24th or worse in five of his final nine tournaments, dropping from first in the standings when the FedEx Cup Playoffs began to a tie for third at the end of the TOUR Championship. 

Koepka will begin the 2019-20 PGA Tour season at the Shriners Hospitals for Children Open starting Thursday in Las Vegas.