The director of aviation safety for the operator reported that, after landing, while parked at the ramp, the pilot-in-command exited the flight deck to open the cabin door. He added that the pilot "found the lead passenger standing in front of the main cabin door waiting to exit the aircraft." He further added that "…[the pilot] was able to open the door from this position, but did not have room to exit the aircraft ahead of the passenger," and as the passenger started down the airplane's air stairs, her foot slipped, she landed on her knees, and she caught her balance by grabbing onto the hand rails. A subsequent medical examination revealed that the passenger had broken her ankle. The director of aviation safety reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.