Chelsea's Danish star has posted a picture on Instagram of herself in a hospital bed giving the thumbs up after having surgery on the back of her thigh.
"It's never fun when things like this happen, but I'm ready to work hard and accept the challenge.
No matter how bad the injury is, I will use it as an opportunity to come back in even better shape when I'm out on the other side," writes the former Linköping star.
How long Harder will be out is unclear, but Chelsea writes on its website that she is expected to be out for a "longer time".