Juan Martin del Potro has reached the quarter-finals of the US Open after Dominic Thiem was forced to withdraw through injury.

Thiem broke Del Potro's serve during the opening game of the match but it soon became apparent that the Austrian was suffering with a knee problem.

After dropping the first set and falling a break behind in the second, he called for the trainer and the decision was made for him to pull out of the match at 6-3 3-2 down.

For Del Potro, he progresses through to the last eight of a Major tournament for the first time since he reached the Wimbledon semi-finals in 2013.

The former champion at Flushing Meadows will now face either Stanislas Wawrinka or Illya Marchenko for a place in the semi-finals.