I had knee arthroscopic surgery july 2013, dr found arthritis in during surgery, and now it hurts to straighten my leg out is that normal?

See your ORS : Not sure how advanced your rheumatoid arthritis is in your knee or the condition of your meniscal cartilages , etc. If your arthritis is progressing weight bearing should be more painful. Pain w/ 'straightening' out your leg may be related to synovial( 'joint lining')inflammation/ hypertrophy often seen in RA patients. See your ors for evaluation or consider getting 2nd opinion. Best of luck!

Very commom: Your symptoms seem to from your knee cap (patella). Chondromalacia patella likely. This responds well to therapy, activity modification and nsaid's.