It depends on what you mean by cramping. Cramping usually refers to muscles and is different than the arthritic and tendon changes seen in moderate to severe RA.
Cramping fingers (and toes), where it feels like your fingers are curling up involuntarily, is called carpopedal spasm
. It could be a sign of low vitamin D, thyroid problems or a malabsorption* of some kind. All of these are common in RA patients. I've had all three!
Only Celiac Disease gave me carpopedal spasms though, I guess my thyroid and vitamin D were caught early enough.
*Malaborption syndromes: basically anything that interferes with digestion and your ability to absorb nutrients: IBS, GERD, Celiac, gastroparesis, Crohn's, etc.