On November 7, 1999, at 1635 central standard time, a passenger on board an Aerostar Raven S57-A balloon, N9130F, suffered a broken arm during a landing in Imperial, Missouri. The balloon was being operated by a commercial rated hot air balloon pilot. The pilot and a second passenger were not injured. The balloon was not damaged. The 14 CFR Part 91 flight was operating in visual meteorological conditions prevailed. The flight originated from House Springs, Missouri, at 1530 cst. The pilot reported the accident occurred during the landing following a hour long flight. He reported he briefed the passengers on the proper landing procedures both prior to and during the flight. He reported he told them how to hold on during the landing, why they needed to hold on, what to expect, how to bend their knees, and how to brace themselves. He reported they began the landing approach at 800 feet above the ground (agl) at which time he once again briefed the passengers regarding the landing. He said he made the final step down at 50 feet agl to a "...gentle glide slope to landing." He reported that just prior to touchdown he again stated "Hold on and bend your knees." He reported that during the normal, stand-up landing, the female passenger, age 83, either failed to or was unable to hold on. She lost her balance and began to sit on the floor of the basket. The male passenger, age 79, then let go of the basket in an attempt to assist her. The male passenger lost his footing and fell on top of the female. It was sometime during this occurrence that the female passenger received a broken arm.