Double-jointedness is a myth. Though you might be able to stretch your muscles twice as far as others, you owe it to a single, extra-flexible joint.
While we humans get concussions pretty easily, bighorn sheep slam their heads into each other all the time without ill affects. How is this possible?
Can you bend your thumb backwards until it touches your wrist? If you join your hands behind your back, can you lift them over your head without letting go?
To say that robots don't have feelings is literal, as well as figurative.
Through the years, it’s been a common misconception that being double jointed is a bad thing. Actually, there is no such thing as a “double joint”. While some people can bend their thumb’s back to touch their forearm, it may appear that they are “double jointed, but there is only one joint at each joint, not two.
If you have good posture, your bones will carry you the way a skyscraper’s frame carries the weight of the building. If not, you may end up more like the leaning tower of Pisa. While there are many routes to bad posture, high heels are certainly one of the most popular.
Contortionists are not able to bend their bodies in extraordinary shapes because they are double jointed, instead they are flexible in several key joints.