• If there is little or no joint swelling, osteoarthritis is the most likely diagnosis. Swelling is a symptom most commonly seen with inflammatory forms of arthritis such as psoriatic arthritis, RA and gout. OA, which results from cartilage deterioration, does not usually involve visible or significant inflammation.
  • If swelling involves the full length of the fingers or toes, think PsA. This condition is called dactylitis, or “sausage fingers.” RA tends to cause swelling over individual joints.
  • If the affected joints are asymmetrical – in other words if a joint affected on one side of the body isn’t affected on the other side –it’s more likely to be psoriatic arthritis than rheumatoid arthritis. RA is typically symmetrical.
  • If joint pain is worse for more than a few minutes in the morning, or after inactivity, consider RA or PsA. With osteoarthritis, pain tends to come after activity; gout comes on rapidly, with intense pain. “If the joint pain or stiffness in the morning goes away after five minutes, then no, I wouldn’t think it’s RA or PsA necessarily. But if it lasts longer than 20 or 30 minutes, I would consider RA or PsA. Osteoarthritis in the morning is usually very brief,” Dr. Matteson says.
  • If blood tests show you are positive for rheumatoid factor, or RF, an autoantibody, suspect RA first. People with PsA are almost always RF-negative. “But there are a few patients who have a very low RF-factor who do not have RA and will not get it,” Dr. Matteson says. RA can develop in people who are RF-positive or -negative.