1. When I was a child, my knee used to lock up sometimes if I had my leg bent. I couldn't open it, and it felt like it had slid out of joint. I still get twitchy if I have to crouch down for more than a few seconds. The last such incident probably occurred in my 20s.
2. I've always had weak ankles, prone to twisting.
3. A few years ago I sat down in the Bronx Zoo and when I stood up again I popped my hip, causing periodic recurring pain and aches - notably this week, where even sitting still on the bus was too much.
4. My sister used to be able to clasp her hands behind her back and bring them above her head to her front without letting go.
5. Yesterday I witnessed my mother casually bringing her foot up to her face to demonstrate that she could. She does that periodically, and at this point I suddenly put together points 1 - 4 and realized - THIS IS ALL HER FAULT! She's got some sort of freaky hypermobility genes, and she passed them on to us, and she and Jenn got the fun parts* while all I got were the twisted ankles and the hip pain! That's utterly unfair, and I told her so right then and there, too. I got completely cheated somewhere.
Edit: I'd forgotten, but well into my teens I used to enjoy sitting with my legs in a W because it was fun
, and likewise I can still catch my foot in my hand behind my back while leaning over. (Though not right now, because my hip is owie.)
* Jenn's flexibility isn't all fun and games, but I'm fairly certain that our mother hasn't suffered one day over this. She doesn't even appear to have any arthritis, and I know that runs in her family.