My right thumb hates me.
While it behaves mostly normally most of the time, it has this stupid quirk. When pushing or exerting pressure with the thumb mostly straight, it randomly says “Hey, f**k you, GameHat.” And it dislocates for a moment. I scream, drop whatever I was doing, and it pops right back in. Then it hurts like a mother for a couple days.
Happened today at work. We have an old, busted up balance. The “tare” button doesn’t work well, so you have to really press hard. Leaning on this thing with my thumb doing the work - pop, the thumb pops out of the joint where it meets the hand, goes sideways, I give a shocked yelp!, it pops right back in, and then I am in a world of pain. Serious pain, for about 10 minutes. Then a serious lingering ache for at least 48 hours.
Interestingly, there’s never any swelling or bruising. But I have done this several times. My most “memorable” was when I was using this thumb to pull off some damp socks. Just using the thumb, pushing down, pop, world of pain.
Why is my thumb so full of fail? Why can’t it just stay in the joint like it should?
Be glad it’s your thumb. My husband’s knee does that trick, exactly as described, with the added benefit of him usually falling down because he can’t switch his weight fast enough to the remaining leg.
Yeah - lots of fun watching a loved one drop with no warning and start writhing in agony on the floor. You have my sympathies.
According to his doctor, he has weak tendons on one side of the knee, letting it pop out easily. He has exercises he does that are supposed to help tighten them up. Perhaps there is something similar you can find for your thumb?
Maybe it just wants to be special. (A lot of us have defective parts, somewhere, that scream for attention every once in a while.)
Thumb therapy? Thumb wrestling, for sure.
Feel better soon.
I have something similar going on in my wrist on the thumb side (basically the next joint down from the thumb.) Except it takes a while to pop back and hurts like hell the whole time. Hasn’t happened in a long time though, I think it’s related to dehydration.
Try shoulder joints. I can sublux my shoulder throwing a tennis ball (or, more likely, a punch at Boxercise).
The worst was 6 years ago, I fell over skiing and really popped my left shoulder. It was midweek, so I spent the rest of the week using the tows onehanded. It took months to come right. Now, I make sure I build up my shoulders in the gym and by swimming, so the joint is well supported and I don’t pop it. It still gets close, sometimes, though.
Oh, and I can do my thumb, too, and knees and ankles and …
My daughter went to an orthopedic specialist for her wrist problems, and he called her hypermobile and said it was genetic. She didn’t talk to me for a week. 
Si
I think my friend’s mother had the same problem (she’s a piano teacher. Is that related?) She saw a doctor and it was solved by stitching something.