Speaking as a massage therapist and musician, I have dealt with problem from both perspectives (though I don't play guitar).

I have found the Blood type diet and related information very useful.

For Blood type Os and Bs especially, but also for some other folks, gluten from grains can be very damaging to the joints as well as often causing celiac problems. According to my uncle's doctor (who was treating him for shingles), 40% of all people of northern European ancestry are gluten intolerant. there are substances in certain foods called lectins which cause damage to various tissues in the body and they are Blood type specific. Glucosamine is effective for joint problems because it blocks the lectins that affect the joints. But if you reduce or eliminate wheat (the main culprit for most people) you aren't putting the lectins in your body to begin with. As someone else said, coffee is another substance that exacerbates the problem.

I discovered this almost 10 years ago. At that time I was beginning to get severe arthritis in my left elbow. About 6 months after it started, I quit wheat, corn, and coffee cold turkey.In two weeks I was painfree without taking anything for it.

I am now 54 and aside from the effects of a severe injury to my right thumb joint which is aggravated almost daily by my massage work, I am not suffering to speak of at all. I still avoid those substances most of the time, and I occasionally take glucosamine, and I sometimes do hand stretches (which as someone already mentioned, are very beneficial). However, I am able to do lots of vigorous gardening work and all the other stuff I do (living in the country and being pretty self-sufficient.) I really believe my eating habits have made all the difference for the strength and health of my hands.

Also as a side note, aspirin and iboprophen have lots of bad side effects for most everyone, especially if taken on a long-term basis.
If you want to help yourself with the pain, topical herbal preparations are your best bet-- Tiger Balm and such-like. If you experiment you'll find something that works.