TromboneChat

Age is like a thief in the night that slowly steals parts of your health.
That thief recently attacked my trombone playing with arthritis at the base of my left thumb.
The carpometacarpal (CPC) joint. Holding the trombone was painful.
I Experimented with different grips, and even a prosthetic hand brace. No relief.
The fix was to increase the mass of the balance weight until the horn balanced perfectly when supported at the first slide brace. Eliminating the nose-heaviness of the horn removed the pressure on the thumb joint, and the pain.
There was only a slight change to the timbre of the sound with the heavier weight; well worth the trade-off.
I hope this info helps somebody else.

I don’t even have arthritis, but I find your recommendation to be very true.

I just sold my main horn for 8 years, and until I get a new horn in late December I have to use my “spare”, which is more nose-heavy than my main horn even it is much lighter overall. My hand hurts. Not only my thumb but other fingers and the palm as well.

That's very interesting.
I've just retired as a guitarist due to arthritis in the base of my thumb and have returned to playing brass (on trombone).
I don't find my arthritis is as painful playing trombone, though I'm now concerned that there may be a time when I have to reassess this too.