"I went to the doctor and, unfortunately, he told me I'm out for the competition," E! News quoted her as saying.
The nature of her injury and how she sustained it were not disclosed.
Because of Webb's unexpected departure from the show, recently eliminated contestant Louie Anderson was given another shot to compete, E! said.
"I've really gotten to know Katherine Webb over the weeks we practiced together. She put all that she could into this, and she wanted to go on but she was truly hurt and in pain. And couldn't!" Anderson said via Twitter.