Thumb Problem - Please Help

My thumb knuckle naturally bends outwards on both hands. I'm 21 and have been playing since I was 4, and primally plays jazz now. However, if my thumbs would relax in a normal manner i would be able to play 9's and 10's more easily. I don't know how I should approach this? I've been playing so many years, and they have not been bothering my playing, and I'm quite skillful, but i do think it would be best if i could fix it.

It looks like you're using a very large amount of unnecessary down force, which would almost certainly exaggerate any problems. Could you post a film maybe, of just slowly lengthening your thumb out into extension? It might clarify whether the limitation is due to physical limits or your conception of how to move. My suspicion is that you're working too hard to attempt to grip inwards and that thinking of opening the thumb into length might help.

As a general rule, sideways angling of the thumb is better than of the fifth. Although we need to do a bit of both, it's a classic mistake to start down the line of the thumb and end up limiting freedom. As a general rule, think of fifth finger forwards and thumb sideways, rather than thumb forwards and fifth finger sideways. Your second photo looks best in this respect, although it looks like you're pressing down way too much.

Here's the video, as requested.

https://youtu.be/-bJrDhQ54Ew Here's the video, as requested. A few thoughts - I'm speculating a little but it looks like you're actively instigating some of the clicks and pops. I speak from related experience as I have some popping and cracking in my own right wrist as well as some thumb issues. With exercises, I have realised that there are places where if I move slower and more sensitively it doesn't necessarily happen. I didn't realise at first, but there was a habit of tightening up and almost enjoying the popping point. In these places, I may still pop a little but I try not to clench or force through that point. It may still give a bit of judder between two spots, but if there's an almighty crunch it's usually because I was actively making it happen, rather than as a result of trying to move smoothly and simply between two points. I say that because I notice that all the movements you do are very quick. It looks like you sense the point of resistance and end up working even harder and forcing through it. I'm confident that you could improve smoothness and control by moving more gently, especially at the point where you sense a tightness. Also, I notice that you have a sense of isolating the movement completely from the arm. Alan's thumb corkscrew exercise would be really good for you, to help make the thumb more of an extension of the forearm. It looks like your movement is tightly shut off by clenching in the wrist. I made a number of thumb exercises myself, which also link the lengthening of the thumb to the rest of the arm. There may be some limit to what is possible but I'm confident you can improve what is possible by learning to free up the places of stiffness and moving in a more unified way, with a much slower and more gentle quality.