Funny you ask :p. Ehlers-Danlos Syndrome is a variant of hypermobility that affects all the joints slowly rendering them incapable of staying in position and so restricting sufferers to wheelchairs or power chairs. Here’s a little about it: http://edsresearch.org/
If you stop by the goals board, you can see it in action :p. I’m to the point where I can still walk with extensive bracing, but not for long and not without consequences :p. I am 47 (well into adulthood?) and have two adult children. However, it’s genetic, so that needs to be taken into account. For a male to be severely effected is rarer, though apparently not as rare if he isn’t white. My youngest son is fine. My older is hypermobile for sure and has experienced joint pain since puberty as I did, though not to the degree as I did, so I have hopes he’ll never deteriorate. Not all sufferers do, and they don’t know enough to determine exactly why it varies.
Don’t know if that is useful, but if it is and you want more, you know where to find me .
She makes the dreams of mechanical devices come true and he dreams of becoming a steamship captain in The Steamship Chronicles, Begin Sam and Nat's steampunk adventure with Secrets, free in all eBook formats. http://margaretmcgaffeyfisk.com/the-steamship-chronicles/