There are some yoga poses that you should probably exclude completely from practicing, as these may be unsafe for people who have rheumatoid arthritis. For example, handstands are particularly dangerous because they put incredible amounts of stress on the wrists and finger joints. No matter how you modify a handstand, the pressure will still exist at these troublesome points.
Before engaging in any type of exercise, it’s a good idea to go over the details of what you’d like to do with your doctor. They can help you determine what’s safe for your body and what restrictions you should practice. It’s important to avoid further damage to your joints and thus worsening any pain or stiffness.
There are people out there who specialize in yoga and have lots of experience working with clients with arthritis. Try to find an instructor who understands your disease and limitations. It’s best to go to an actual class, rather than watching videos on TV or the Internet. Always tell your teacher about your limitations before starting any class.