Dear Louise
Please dont assume anything regarding the neck area with RA, go and get it checked out with GP or rheumy. It may be muscular, but RA can cause changes in the cervical spine that need looking at seriously (x-rays, scans etc).
I have had severe RA for nearly 40 years and had two cervical spine fusions and just about to have another. Have had nerve blocks under CT scanning into the neck today. They can do lots to help neck pain so do ask, it's important.
In the meatime hot wheat bags between the shoulder blades and lying down to take the weight off the neck helps, plus all the pain relief you can tolerate!
Good luck Louise and let us now how you get on.
Take care,
Lizx