Get creative to avoid putting stress on your painful joints. Let go of your traditional sexual position if it hurts.
Also, try props like pillows or cushions to support your hips, shoulders, neck, or back. Or add a vibrator for stimulation during foreplay. Many women have vaginal dryness as they get older. It's also a problem if you have Sjogren's syndrome, a condition often seen with rheumatoid arthritis. If you have that, try vaginal lubricants, vaginal moisturizers, or vaginal estrogen creams.