I had an arthroscopy on my knee for rheumatoid arthritis three months ago. th eknee is still painful and swollen. why?

Depends: Arthroscopy can only help you if you have any structural abnormality like a meniscal tear. Ra is an autoimmune that can prematurally destroy a joint. You may need some form of oral treatment for RA if you are still symptomatic. You should follow up with your rheumatologist.

Rheumatoid: Patients have arthroscopies for inflammatory diseases such as ra, but this illness can return rapidly to the joint even if the surgeon cleaned it out well. I do not think your knee should be so painful simply from the procedure since it has been 3 months, but some peolple heal slower. My suspicion is that RA is active in the knee and may require medications rather then further surgery.