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Madonna often invites bone-breakers on tour.
Bone-breakers are known for dislocating their shoulders to create fluid movements that are spectacular to watch - but also might make you a bit squeamish.
Instagram users are loving it, though. Dancers have uploaded more than 7,000 posts under the hashtag #bonebreaking, with 4,000 more under #bonebreak.
Bone breaking has its roots in Brooklyn, where young dancers regularly compete in dance competitions such as Battle Fest, according to a blog post from Opening Ceremony. It is a type of flex dancing, which is a contortionist style of dance.
Flex dancers have competed in Brooklyn since at least 2006, according to the New York Post. Another competition will take place on July 26.
While many hold the misconception that bone-breaking evolved from hip hop dance, it actually emerged from a Jamaican dance style called bruk-up, according to a recent video exploring bone breaking in The New Yorker.
Busta Rhymes has featured bruk-up dancers in his music videos, and on Madonna's MDNA tour in 2013, six of her 22 dancers were bone breakers.
Fellow Madonna dancer Stanley Mondesir isn't double-jointed. He told Opening Ceremony that it took plenty of stretching and practice to build up his skills.
Either way, bone-breaking isn't exactly easy on the body. Henderson recommends using Tiger balm to ease soreness. He also takes baths in Epsom salt.