Thousands of people in China are making "finger knots" to show off the flexibility of their fingers. The "finger knot" requires someone to interlock their digits to form a knot.

Chinese TV personality Li Sisi posted a photo of her trying the challenge onto her Weibo, China's equivalent to Twitter. She wrote, "If you tried twisting your fingers like this after reading this post, raise your hand."

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Weibo users have been quick to share pictures of them doing the difficult hand trick.

The new social media craze has spread quickly and caught the attention of the media. They even made a video to teach viewers how to do it.

Web users around the world also gave the hand trick challenge a go and shared pictures of their attempts on Instagram and Twitter.

Dr Jane Simmonds, a registered physiotherapist at the University College London, said those who could perform the difficult finger tricks are likely to have joint hypermobility, a common phenomenon present in 20 to 30 percent of the general population, according to the Daily Mail's report.

As Dr Simmonds said, joint hypermobility is more common in children and females, and also in Asian and Afro-Caribbean ethnic populations, which may be a reason for the popularity of finger tricks in China.

Daniel Brown, a consultant hand surgeon at The Bone & Joint Centre at Spire Liverpool Hospital, said only a small number of people can do the finger trick that Chinese actor Zhang Yishan has performed.