I would also add that, many guitarists hardly use their pinky finger. Watch Eric Clapton. He hardly uses his pinky. Eric Clapton is still touted as a Guitar God today. Django Rheinhardt only had TWO FINGERS! He is a legend.

Physical limitations will have their due. You work with the tallent and dexterity that you brung to the table. How far you can go with that tallent is unanswerable until you try. If you can't accomplish some skill now, don't let it stop you from continuing to developing your ablities as far as you can. Arthritis or not, every player deals with limitations. Some get much farther than others. In this regard Attitude may not the do all, be all. But you will never get out of the gate without it.