In March 1984, Benoit injured her knee severely during a 20-mile training run, forcing her to undergo arthroscopic knee surgery just 17 days before the United States Olympic Women's Marathon Trials were scheduled. However, she recovered from the surgery much more quickly than expected, and was the favorite in the trials, at Olympia, Washington. She beat runner-up Julie Brown by 30 seconds, winning in 2:31:04. Three months later, she competed in the 1984 Summer Olympics in Los Angeles, winning the first Olympic Women's Marathon in 2:24:52, several hundred meters ahead of Grete Waitz, Rosa Mota, and Ingrid Kristiansen.