Kaley Cuoco is sharing details about the time she almost lost her leg in a horseback riding accident a moment that Big Bang Theory creator and producer Chuck Lorre called the darkest, most frightening time in the sitcoms history.

In a Vanity Fair book excerpt from the The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series by Jessica Radloff, Cuoco and her co-stars recalled the accident.

In 2010, Cuoco, an equestrian, fell off her horse and the animal landed on her left leg. She was rushed to the hospital where Lorre happened to run into Dr. Stephen Lombardo, a highly regarded orthopedic surgeon. Dr. Lombardo facilitated a quick operation with the best surgeons available, according to People .

But Cuoco faced a grim possibility.

Before I went into surgery, they made me sign something that said, We dont know until we get in there and see this leg, and it could come out that you dont have it anymore, she said in the excerpt.