A 19-year-old Chinese girl has gone viral after posting a video demonstrating her unusual ability to pop her kneecaps out and then back in painlessly because of a condition she was born with.

The unnamed girl from Jiangssi claims that she never even knew her kneecaps were special until schoolmates saw her popping them out of their sockets randomly and then casually popping them back in. Some of them freaked out and told her to see a doctor, but her knees had been like this for as long as she could remember. Nevertheless, she decided to follow her friends’ advice and see a doctor, who confirmed that she had congenital “patella dislocation”, which caused her patellas (kneecaps) to pop out randomly and pop back in just as easily. The physician said that the condition was rare in girls, but reassured the youth that, as long as it didn’t cause her pain or impede with day-to-day activities, it wasn’t a problem.