I’m wondering, I definitely can’t bend my thumb like the one in the picture, is it double jointed or is that something else? 
Yeah. I can do the same thing.
Isn’t that just a normal thumb doing a normal thing? What am I missing?
Where the thumb leaves the base of the hand, I cannot make my joint go that far away from the rest of the fingers (That is the best way I can describe it), I don’t think most people can.
I’ve always done it, taking it for granted, and am surprised to learn that anyone can’t. I play piano and guitar FWIW…
Just in case you were unaware, no one is actually “double jointed”. The wiki on hypermobility has some pictures that might make one cringe.
My thumbs do that, also. I used to make the coolest finger gun on my block as a kid. Also puppy ears for shadow puppets.
ah, so thats what I do with my shoulders is called. wow it really is icky to see on someone else
It’s a hypermobile metacarpophalangeal joint. I can do that too. Basically, the joint can swing back farther than normal people.
I’ve always thought it was my mutant X factor. Too bad the Xmen don’t need a guy whose main superpower is being able to do the “I pulled off my thumb!” trick really well.