Yep, I`ve just started to get arthritis in my left thumb, I`ve found that playing a Jazz width neck is easiest on it but bizarrely playing my thickest necked Precision is also ok, it`s the medium sized necks I`m having trouble with so it`s clearly how I position my thumb on those that`s the issue. As such I`ve got a bit of work and many years of unlearning to do.