Realizing that GuestAlley may not check this thread, given that it started in ought-six, I have two suggestions:

Medically, I second the glucosamine idea, although it's been getting mixed reviews here on Mudcat.

Musically, I suggest trying an alternate tuning like open G, which is
DGDGBD. Majors are straight barres, which still takes some effort but the forefinger will be straight and you can lay the middle finger over it and press with both. (G is open; C is across 5; D is across 7)

Sixths and sevenths can be pinkied on to the high D string two or three frets above the barre; like 777779. If you want more chords in that tuning, buy yourself a simple banjo chord chart, because standard-tuned banjo is also an open G. (I use that idea myself, not because of arthritis, but because I can then play songs scored for banjo on my guitar or my dobro, and get a better sound.)

If you play in a minor key a great deal, then tune the B down to Bb:
B-G-D-G-Bb-D. But remember if you want to play a major chord while in that minor tuning, you have to finger the B-string one fret above where you otherwise would.

If your voice is such that you're in C most all the time, you could tune to an open C, which could be E-G-C-G-C-E. If you go that route, you're on your own for chord forms, but if you chose to pursue that avenue, I'm sure you can find forms somewhere.


CC