Perri Shakes-Drayton failed to add to Britain's medal tally at the World Championships, complaining of a knee injury as she finished seventh.
The 24-year-old faded badly after hitting the third and fourth hurdles.
"In the race it felt like my knee was wobbling," said Shakes-Drayton, whose time of 56.25 was nearly three seconds shy of her personal best.
Fellow Briton Eilidh Child was fifth (54.86) in a race where Czech Republic's Zuzana Hejnova won gold.
The 26-year-old Czech, the dominant athlete of the year, eased to victory in a world leading time of 52.83.
"I'm gutted," said Shakes-Drayton, who will miss the 4x400m relay after returning to the UK on Friday to get the knee fully assessed.
"I was doing so well and felt so good in the heats and semi, but tonight after the first bend I was just going back and back and back," added the Londoner, who was appearing in her first major outdoor final.
Dalilah Muhammad (54.09) took silver while her fellow American, the defending champion Lashinda Demus, claimed bronze in 54.27. Both times were slower than the personal best of 53.67 Shakes-Drayton set at the Anniversary Games last month.
Child ran down Shakes-Drayton on the home straight to beat her team-mate for the first time, but she could not manage the personal best she had set her sights on.
"It wasn't a great race, I lost my stride on the back straight," said the 26-year-old Scot. "I did feel a bit tired but I cannot complain with a fifth in the world final."
There were to be no medals for Britain on the sixth day of competition in Moscow's Luzhniki Stadium.
Robbie Grabarz cleared 2.29m, the height which won him bronze in London 2012, but the event has reached new heights in the last 12 months.
Seven athletes finished above Grabarz in an engrossing final, with Bohdan Bondarenko's winning jump of 2.41m a championship record.
"I'm not jumping over the moon or anything but it's eighth place in a World Championship final and with the run in I've had it's acceptable.
"It was a brilliant atmosphere. I genuinely enjoyed it and it was great fun. It was amazing to see that much support behind Bonderenko and it was just great to jump in that atmosphere."
In the women's 1500m final, a strong finish from Hannah England earned the 2011 silver medallist fourth place, but the Oxford athlete was some distance behind Sweden's gold medallist Abeba Aregawi.
"I don't think I left it too late, I'm not sure I could have got those three anyway," England told BBC Sport.
"Fourth in the world is amazing. If anything it's backed up my silver form two years ago. I know I should be gutted with fourth but I'm really chuffed. I'm really proud of myself."
Jodie Williams, the 19-year-old former world junior champion competing in her first senior outdoor championships, went out in the semi-finals of the 200m. She finished in seventh place in 23.21.
"It's tough, especially when you've given it everything you've got in the morning heats, to come and have to do that again a few hours later," said Williams.
"But it's a massive learning curve for me. I'm used to being favourite or close enough to the top to be able to take the rounds much slower and save my energy, but this is a completely different world so you need to give it everything you've got in every round."
Britain's 4x400m men did progress to Friday's final, finishing second behind Jamaica in their heat to clock the fourth quickest time of qualifying and a season's best 3:00.50.