Hypermobility

Hypermobility Syndrome/double jointed/Overflexing/hyperextensive call it what you will and ASD seems to go hand in hand; I've heard so many parents comment on the uber-bendiness of their child's joints, the high number of dislocations and sprains.
Couple that with the often high pain threshold of ASD and you can get a dislocation or inflamed joint that barely registers on the kid's horizon for the day.
And it certainly doesn't get in the way of all that physical activity they get into.
Until something gives.
My own Aspie teen has frequent cramps, the urge/need to crack his knuckles and 'pop' whichever joints are bugging him.
When he was younger we woke up to find he'd flexed his hip joint until it trapped a nerve in the night.
First warning we had was he just wouldn't get out of bed the next morning.
No tears, no tantrums, no yelling, no pain.
He just wouldn't weight-bear.