The 24-year-old's leg appeared to give way on impact as she hit the icy landing slope after losing control on a big jump.
She turned cartwheels before coming to rest and received lengthy medical attention then was taken off the course on a stretcher.
"Anna Woerner has suffered a fracture of the tibial plateau in her right knee in her fall. The injury is currently not being treated by surgery," the German Ski Association said via its Twitter account on Friday evening.
Chile's Stephanie Joffroy also needed a stretcher to get off the slope after falling in the next quarter-final but, although she was also taken to hospital, a wave as she went past the crowd indicated she was not too badly hurt.
Safety concerns were high after Russian free skier Maria Komissarova fractured a vertebra and dislocated her spine during practice on the same course at the Extreme Park last week.
"The course is tougher than some World Cup courses. The jumps are bigger, but still, if you land the jumps it is nice and smooth," said Sweden's Sandra Naeslund, who was knocked out in the semi-finals on Friday.
"There are crashes sometimes, that is the sport."