Koepka defeated Peter Uihlein on the third play-off hole at Royal Greens Country Club to win for the first time since the WM Phoenix Open in February last year.
The former world number one has been plagued by injuries in recent years and revealed the extent of the problems in post-round interviews.
"I didn't know if my career was over for a half second," Koepka said. "I told Claude (Harmon, his coach) that I wasn't sure if I was going to play. It's nice to be able to come back and to be able to win.
"The last two years haven't been fun. It's been a long road.
"It's been before LIV, when I blew my knee out and my foot was pointed that way, almost backwards and sideways.
"I mean, eventually I'm going to have to have a knee replacement in a few years, but I wasn't sure whether I could even move the same way and if I want to play if I could move the way I wanted.
"I'm fortunate (to) be in the spot that I'm in right now."