Simpson was contending before the mishap about halfway through the race.
American Dan Huling takes fifth in 3,000m steeplechase.
Check out these photos from a hot, humid day in Beijing.
The event should offer a compelling sneak preview of the 2016 Olympics in Rio de Janeiro!
Implement Loxsom's tips to get ready for your own upcoming big races.
He will move up to the 26.2-mile distance next spring in London.
American runners had a good showing last week in Moscow!
The United States won at least one medal in all four middle distance finals.
The Brit grabbed gold in the 5,000m on Friday night.
The American captured her second career world championship medal on Thursday night.