Strictly Come Dancing's Artem Chigvintsev danced on last weekend's show without realising that he had fractured his spine.
The 29-year-old, whose dance partner is Australian star Holly Valance, suffered the injury last Friday while rehearsing for the BBC1 programme.
But the injury was initially diagnosed as a strained muscle and it was not until Monday that medical results revealed the condition - a transverse process fracture of the lumbar spine.
The pair's jive scored 34 out of 40 at the weekend, the second highest of the night, despite the pain the dancer was in.
Chigvintsev, who won the Strictly Come Dancing glitterball last year with former EastEnders actress Kara Tointon, may have to pull out of this weekend's show.
Former Neighbours actress Valance, 28, is now training with New Zealander Brendan Cole, who could perform with her this weekend, after his celebrity partner, Lulu, was voted off.
The BBC said in a statement: "Artem injured himself during rehearsals on Friday.
"Following medical attention, he has been diagnosed with a transverse process fracture of the lumbar spine. We have been told that this sort of fracture is completely stable and he has been advised that there is no untoward effect from him continuing to dance.
"We will, of course, continue to review this following medical advice over the course of the week."
Chigvintsev, who became romantically involved with Tointon following last year's show, wrote on Twitter: "Thank you for all your get well wishes."