Psoriatic Arthritis

Psoriatic arthritis (PsA) affects joints (such as the knees or those in the hands and feet), as well as areas where tendons join to bone (such as the heel and lower back). Most people who have psoriatic arthritis find it occurs after developing skin psoriasis, but some do develop the arthritis before they notice any psoriasis on their skin.

Although having psoriasis means you are more at risk of developing psoriatic arthritis, it is not always linked to how severe your psoriasis is. People with mild or moderate psoriasis can also develop psoriatic arthritis, which is why it is important to be aware of the symptoms.

As with psoriasis, a family history of the condition does not necessarily mean a person will develop psoriatic arthritis.

Have a look at our information leaflet on psoriatic arthritis for more information.

In psoriatic arthritis, the joints affected may become tender, swollen and stiff. These symptoms tend to be worse first thing in the morning and with rest, and ease with exercise.  Inflammation of tendons without obvious inflammation of the joints can also occur in psoriatic arthritis, which makes it easy to misdiagnose as tendonitis or tennis elbow, for example. Psoriatic arthritis commonly affects the small joints of the hands and feet, and so a swollen sausage-like finger or toe is another common sign.
Nail psoriasis is seen in a large number of people with PsA, so this can also be a good indicator. Like psoriasis, PsA can wax and wane, so people with the condition may find that their symptoms get better and worse over time.

There is no conclusive test for psoriatic arthritis, and it can therefore be a difficult condition to diagnose.

Psoriatic arthritis is an inflammatory joint disease closely associated with psoriasis, which affects the joints and tendons. ‘Inflammatory arthritis’ means that there is inflammation present in the affected joints, rather than just wear and tear. It can be difficult to diagnose, as symptoms can be similar to other types of arthritis, and a patient does not necessarily have to have psoriasis to develop it. It is also possible for people with psoriasis to develop a different type of arthritis (such as rheumatoid arthritis or osteoarthritis); the fact that they have psoriasis does not alone mean their arthritis is psoriatic.

How is it diagnosed?

At present there are no definitive guidelines for diagnosing psoriatic arthritis; a doctor will make a diagnosis based on symptoms and medical history, and by ruling out other conditions. Usually, a blood test will be carried out to test for rheumatoid factor (the antibody found in rheumatoid arthritis). This is usually negative in people with psoriatic arthritis, although a positive result can be due to causes other than rheumatoid arthritis. A doctor may also use X Rays, ultrasounds or other scans, such as an MRI to look at the patient’s joints. These scans often show inflammation or areas of new bone growth with poorly-defined edges in people with psoriatic arthritis.

Traditionally, the Moll and Wright (1973) criteria have been used to diagnose psoriatic arthritis. The criteria are: an inflammatory arthritis, the presence of psoriasis, and a blood test negative for rheumatoid factor. Although this criteria set is still used, it does have limitations, for example, psoriatic arthritis can occur without there being current psoriasis on the skin.

For more information on diagnosing psoriatic arthritis, have a look at our information sheet.