One of the frontrunners on this season of Dancing With the Stars may have become set back by a knee injury.

Pro dancer Derek Hough revealed in his TV Guide column Friday that his celebrity partner Amber Riley (Glee) has had pain in her knees this week. This means that they have not been able to rehearse until Friday, just three days before the next episode of DWTS.

"We are really, really behind!" Hough admitted. "Amber's knees have been acting up, so we haven't been able to rehearse at all. She got them drained the other day, so we're finally going to start rehearsals today and see how that goes."

Hough went on to explain that Riley had not been injured; rather, she had a buildup of pressure in her knees. He said that they will be performing the tango on Monday night's show but they have not done any choreography yet.

Despite their approaching deadline, Hough said that Riley's health matters most.

"I just want Amber to be OK," he wrote. "Health is the most important thing. Right now, our concern is to see if it's just pain that will go away or if it's pain that's going to do more damage if we continue."

If Riley knees become a serious injury, she would be the second contestant this season to have knee trouble after TV scientist personality Bill Nye. The "Science Guy" was injured in the week leading up to the Sept. 30 episode but performed anyway. Nye and partner Tyne Stecklein were eliminated from the competition the same night.

The next episode of Dancing With the Stars airs Monday, Oct. 7 at 8 p.m. on ABC.

Watch Riley and Hough's latest dance here:

Tags
Dancing with the Stars, Dancing With the Stars Season 17, Amber Riley