Man's knee bends the wrong way after getting kicked by Muay Thai instructor

A disturbing video online shows a man's knee bending backwards after getting kicked by a Muay Thai instructor.

In the video that was posted on YouTube by TomoNews US, both men can be first seen on a mat at a gym.

The instructor was gesturing at the man's body while explaining what he was going to do.

Thereafter, he executed a hard kick on the man's left thigh.

The latter's knee then bent backwards following the blow. He could not stand upright because of what happened and fell onto the mat.

Although the accident was one that is hard to watch, people around the duo can be heard laughing for some reason.

Towards the end of the video, the man's knee apparently popped back into position after the instructor kicked the back of his leg. It is unclear though, if he sustained any lasting injury.

The video was reportedly filmed in 2012 but was posted on YouTube in 2016.