Double-jointedness is a cool party trick that elicits many "oohs" and "aahs." Yes, anytime that a person can bend their fingers to touch the back of their hand, bend their knee joints backwards, or otherwise contort their limbs into unusual and painful-looking poses, we are mesmerized with morbid curiosity.
The condition is known as hypermobility syndrome, and it describes the ability to move or stretch a joint outside the typical limitations without any pain. Surprisingly, the condition is common, showing up in between 10 to 25 percent of the population. So the chances of encountering a double-jointed act at a party is statistically pretty good.
Of note, the term 'double-jointed' is misleading since it implies that these peoples' flexibility is due to them having more joints than normal. But, that is not typically the case, and most 'double-jointed' people have the same number of joints as other people.
