MASON, Ohio — A little more than a week before she is to begin defending her United States Open title, Naomi Osaka injured her left knee and abandoned a quarterfinal at the Western & Southern Open on Friday afternoon.

In the third set of a match against Sofia Kenin, Osaka appeared to have taken control, winning six of eight games before jamming her knee as she landed on her service motion. Osaka then walked to her chair to receive medical attention, and after an evaluation, her knee was taped.

She returned to the court 10 minutes after she left, playing two more points haltingly, losing both, and then stoping to give Kenin a 6-4, 1-6, 2-0 victory.

Osaka, 21, limped into the interview room an hour after the match, with an ice pack strapped to her knee. When she reached the stairs leading to the podium, Osaka smiled wearily, then used her arms to hoist herself up.