In UK hip replacements are not usually offered for RA damaged joints
Really? I know someone with RA who has had both hips replaced- and several other bits.

From Arthritis - NHS choices:

Hip replacement is the most effective treatment for a hip joint that causes pain and cannot function properly. The most common reasons for surgery are:

Osteoarthritis. This is the most common form of arthritis. It occurs when connecting tissue between the joint is damaged, causing bones to rub together painfully.

Rheumatoid arthritis. This is caused by the immune system attacking the lining of the joint, resulting in pain and stiffness.