Hi Julie,
I have not heard of anyone using a knee support because of ra.
My sister has a knee support, and she also has ra, but she had a nasty accident a bout 4yrs ago and smashed has knee and her surgeon suggested the support, nothing to do with rheumatology.
She had her knee measured etc. etc.
I would ask your rheumatology team about using one to see what they suggest, just to be on the safe side.
Zena x