Could Brooks Koepka miss U.S. Open with knee problem?

Two-time U.S. Open winner Brooks Koepka could miss this year's tournament due to a knee issue that caused him to withdraw from the weekend's Northern Trust at TPC-Boston.

As ESPN's Bob Harig wrote, Koepka is also dealing with a lingering hip problem this summer. He missed the cut last week at the Wyndham Championship and seemed out of sorts.

"My golf swing's fine," the 30-year-old said after that disappointing result at Sedgefield Country Club. "If I can physically do it, then yes, everything's fine."

Harig and the Associated Press (h/t ESPN) documented how Koepka underwent stem cell treatment on his patella last August. He aggravated that injury during an October tournament, and it's unknown if he's been 100% throughout a 2020 calendar that was drastically altered in March due to the coronavirus pandemic.

Koepka won't have long to get right and healthy. The U.S. Open held at Winged Foot Golf Club in Mamaroneck, N.Y., begins Sept. 17. The competition will take place without fans on the course because of the coronavirus pandemic.