(My left index finger hurts, too, especially above the first knuckle, and my left pinkie is in even worse shape. Just part of the aging process, I suppose (arthritis, to be specific). Maybe I'm dull and unimaginative, but I can't see that playing a guitar with a narrower neck would make very much difference. Not playing at all might help, but for me that's not an option ~ at least, not yet.)


I agree with PoopaGator.

I play very thin neck Brook Guitars (OM and 000 types) and my fingers hurt in exactly the same places as described.
I play softer and that seems to help - the thin neck means that I don't get pain at the base of my thumb on the left hand though.

I believe the problem is fundamentally what my mate (also born in the 50's) calls "rust".