Interesting question - no smart answers here. I recently got one small osteo-arthritis in one bone in my hand seemingly as the result of a minor fall. I had screaming pain moving all over my hand, thumb and arm for nine weeks and that drove me nuts. Part of my identity always has been physical flexibility and strength and suddenly I had no answers about is this permanent, how long will this go on, is it getting worse, why does my upper arm hurt at one moment and my thumb the next. I was misdiagnosed and had to experiment with when to rest, when to splint, how to self-care.

I'm not surprised that full blown arthritis could drive someone nuts.
Coincidentally I came across a wonderful, compassionate article about newly diagnosed arthritus sufferers called "Disruption and Chronic Illness". It talks about disruption of sufferers' sense of identity and the impact on their relationships and working life. Particularly because arthritus is an illness which stretches medical science and social support to it's limits because it's not predictable. I really relate to the concept of disruption by physical limitations = shaking the sense of self and social relationship to the foundations.