Serena Williams remains on course for a record-equalling 24th Grand Slam title despite needing medical attention in a win over Petra Martic at the US Open.

The American, 37, reached the quarter-finals in New York with a 6-3 6-4 victory against the 22nd seed.

The six-time champion needed her ankle restrapping in a medical timeout after turning awkwardly during the final set.

Williams was able to return to the court at Arthur Ashe Stadium to see off the Croat in dominant fashion.

Speaking about the injury, Williams said: "I just rolled it, I don't know why. I was volleying and it just went over - that was frustrating but I wanted to get it compressed really fast.

"It affected me a little mentally because I've had a rough year with injuries."

Williams faces China's Wang Qiang next after the 18th seed beat world number two Ashleigh Barty in the last 16.

She will move level with Margaret Court on the most Open era Grand Slam titles if she wins at Flushing Meadows.