Violinist Lindsey Stirling is one of the favorites to win the mirror ball trophy on "Dancing with the Stars" this season — but in a sour note, she's suffered a serious rib injury.

On Monday night's show, viewers saw Stirling reveal how she displaced a rib during last week's dress rehearsal.

She and partner Mark Ballas got through their sci-fi-themed dance for movie night, but this Sunday she appeared to aggravate the injury and moaned to him, "It hurts! I can't even rehearse because I'm in so much pain."

Ballas took her to urgent care, where Stirling nervously asked him what would happen if she couldn't dance. The longtime "DWTS" pro said that would mean they would forfeit and have to leave the competition.

However, Stirling was cleared to dance and delivered a fast-paced Paso Doble based on the Day of the Dead, in which she had to slide across the floor on her knees.

Ballas and host Tom Bergeron had to help her up off the floor at the end of the dance as she appeared to collapse. Stirling crouched on her partner's knee and complained again of pain before getting the judges' critiques.

Carrie Ann Inaba praised her bravery and Bruno Tonioli marveled, "You managed to do it!"

Stirling wasn't able to complete post-show interviews but Ballas told reporters afterwards, "She's doing better. I told her she needed to go put ice on [her rib].

"We took the X-ray yesterday and I was nervous…because if it was a break or a fracture that would have been a huge problem. There's no break, no fracture, so they call it a floating rib. I can't give you the professional diagnosis of what that is…I know that the muscles between the ribs are really painful.

"Luckily, she's in a state where she can continue [on "DWTS"] as of now," he said.

Ballas noted that it seemed like a freak injury: "It's funny. You always seem to hurt yourself doing dumb s--t….I think she [just] lifted her arm and it went, bup!"

The dancer emphasized, "Her health comes first. I'm nervous about her being OK. Thank God it looks like she'll be able to continue."

Ballas is making sure Stirling, who has thrilled YouTube viewers with her violin, gets enough rest and that she's "chilling."