China's Liu Xiang went into the 110m hurdles looking for redemption for an injury withdrawal in the event in 2008, when he was the defending Olympic champion. Alas, he he suffered another injury on this stumble over the first hurdle in the first qualifying round.
In case that crash doesn't look horrific enough for you, here it is from the side angle, where you can see Liu crumple to the ground.
Liu was forced to hobble to the finish — though he officially earned a DNF for the heat — and was helped off the track in a wheelchair. Chinese track coach Feng Shuyong thinks Liu may have torn his Achilles tendon. But Feng is not sure whether the injury will mean retirement for his star:
"It is hard to say. Lots of athletes get injured and come back. It depends on many factors. I hope all the fans can understand this and that anything can happen. It happens to many athletes."
Liu took gold in the 110m hurdles in Athens at the age of 21, but if he is to return for the 2016 Olympics in Rio de Janeiro, he will be 33 at the time of competition.