Ahn mentioned on his personal website that the pressure was too much for him and he contemplated quitting the sport. Due to the issue, KSU stated that starting next season, the team would be united under one head coach to prevent deleterious rivalries. At the 2007 World Championships held in Milan, Italy from March 9 to March 11, 2007, Ahn won his fifth world championship, finishing first in the 1,000 m and in the 5,000 m relay with teammates, Sung Si-bak, Song Kyung-taek, and Kim Hyun-kon. He also won silver in the 3,000 m behind his compatriot Song Kyung-taek, and won two bronze medals in the 500 m and the 1500 m. He is the first man to win five world championships. Ahn is the only male short track skater to have won at least three consecutive world championships (having won five in a row); Canadian short track legend Marc Gagnon has won four times, but his titles did not come back to back. On January 16, 2008, the Korean Skating Union (KSU) announced that Ahn had injured his knee after colliding with a fence during national team training at the Korea Training Center in Taeneung. After being sent to the hospital, the injury was diagnosed as a fractured knee. Due to the injury, KSU announced that Ahn would not be competing in the ISU Samsung World Cup Series 5 and 6 in Quebec City and Salt Lake City, respectively. It was also reported that he would not be competing in the 2008 World Championships in Gangneung or the 2008 World Team Championships in Harbin, China. As a result of the unexpected injury, it was clear that Ahn would be unable to defend his sixth World title, leaving his countrymen Lee Ho-suk, Song Kyung-taek, and Lee Seung-hoon to make up the ground. After undergoing three surgeries, his rehabilitation period was predicted to be around 2–3 months. After eight months off the ice, a South Korean news article reported on September 5, 2008 that Ahn was back training, undergoing approximately two hours of physical reinforcement and skating along with around five hours of rehabilitation accompanied by muscular power training. The article also reported that Ahn was eyeing the 2010 Winter Olympics in Vancouver, Canada. Because of his injury, Ahn did not compete in the 2009 World Championships in Vienna, Austria which took place March 6–8. During the South Korean national team trials, which ultimately determine the Fall World Cup and Olympic Teams, Ahn was unable to qualify, finishing 7th in overall points (because Ahn did not compete in the last two World Cup seasons, he needed to finish in the top three in overall points to qualify).