'Dancing With the Stars' Contestant Patti LaBelle Continues Struggle With Knee Injury

— -- "Dancing with the Stars" has been difficult for Patti LaBelle.

The singer has been complaining of a sore knee, and last week, things took a bad turn.

"I never thought this journey would be this tough," LaBelle said in a sneak peek of this week's episode. "First of all, the [waltz] is not an easy dance and you're twirling and turning."

At one point, the singer, whose rehearsal time was cut short due to the injury, debated not dancing.

"I want to be here," she insisted, though she was clearly in pain.

LaBelle and Artem Chigvintsev are supposed to waltz to the "Pinocchio" song "When You Wish Upon A Star" tonight.