Pauline, Charlie had the same problem and he would just explain and refuse the handshake. When Joshua was very young we were teaching him to shake hands with the male members of the family, he would just put one finger out to Charlie as he knew Granddad had painful hands. Arthritis is such a painful thing, after years and years of marriage I had to sleep in a separate bed because if I turned in the night and touched Charlie's legs he was in agony.
Hope your hand is less painful tonight.