Actress Park Si Yeon, along with Lee Seung Yeon and Jang Mi In Ae, were all recently accused of using propofol -- a hypnotic agent commonly used in anesthesia. It’s known to make one feel good and refreshed, so some celebrities have been caught using it illegally.

While being investigated, it was revealed that Park Si Yeon’s been suffering from a disease known as avascular necrosis. The disease causes a blockage of blood circulation that causes cellular death in bones. Park Si Yeon got this disease from an injury while filming The Fox Family.

So the disease that Park Si Yeon wanted to hide so badly had to be revealed to defend herself from the illegal use of propofol. Park Si Yeon’s party claims that it was prescribed by her doctor for her avascular necrosis treatment.