Diagnosis

During the exam, your doctor might:

• Examine your joints for signs of swelling or tenderness
• Check your fingernails for pitting, flaking and other abnormalities
• Press on the soles of your feet and around your heels for to check for tender areas

No single test can confirm a diagnosis of psoriatic arthritis. But some types of tests can rule out other causes of joint pain, such as rheumatoid arthritis or gout.

Imaging tests

• X-rays. These can help pinpoint changes in the joints that occur in psoriatic arthritis but not in other arthritic conditions.
• MRI. This uses radio waves and a strong magnetic field to produce detailed images of both hard and soft tissues in your body. MRI can be used to check for problems with the tendons and ligaments in your feet and lower back.

Laboratory tests

• Rheumatoid factor (RF). RF is an antibody that's often present in the blood of people with rheumatoid arthritis but not usually in the blood of people with psoriatic arthritis. This test can help your doctor distinguish between the two conditions.
• Joint fluid test. Using a needle, the doctor can remove a small sample of fluid from one of your affected joints — often the knee. Uric acid crystals in your joint fluid might indicate that you have gout rather than psoriatic arthritis. It's also possible to have both gout and psoriatic arthritis.