Photo: Karwai Tang

Usain Bolt crumpled on the track with a left leg injury as he was chasing gold in the 4×100-meter relay at the world championships.

Instead, Britain upset the United States to take gold in 37.47 seconds. The Americans were .05 seconds behind. Japan took bronze in 38.04.

According to the Jamaican team doctor, Kevin Jones, Bolt had a cramp in his left hamstring.

Bolt grimaced in pain as he was running down the finishing straight before stumbling and falling to the track.

“A lot of the pain is from disappointment from losing the race,” Jones said. “The last three weeks have been hard for him, you know. We hope for the best for him.”