Psoriatic arthritis is a form of psoriatic disease. It can lead to symptoms in the skin, nails, and joints. Imaging scans, such as X-rays and MRIs, can help diagnose psoriatic arthritis and show if damage has occurred inside the body.

Psoriatic arthritis (PsA) is a chronic form of arthritis, an inflammatory condition that can worsen over time. However, treatment can help slow the progress of PsA and prevent permanent damage in the joints and tissues.

Around 47% of people with PsA experience damage that is visible in imaging tests within 2 years of a diagnosis.

Imaging tests can help ensure an early diagnosis and help monitor the progression of PsA.

Early diagnosis and treatment can help slow the progress of this disease.

Blood tests for PsA may show high levels of inflammation, but they can also be within a moderate range.

For this reason, doctors may recommend imaging tests to help confirm the diagnosis.

These tests aim to show the disease progression and the type of damage, which will allow doctors to determine the right course of treatment.

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X-ray showing bone erosion due to psoriatic arthritis.
Image credit: MyArthritis/Flickr

An X-ray may reveal bone or joint damage, such as:

  • a “pencil-in-cup” structural change in the bone
  • the erosion or destruction of bone tissue, known as osteolysis
  • spaces narrowing in a joint
  • new bone formation

If PsA affects the vertebrae, bone and joint changes will appear as follows on an X-ray:

  • asymmetrical
  • bulky
  • randomly in your vertebrae, for example, skipping levels

In the early stages, changes may not be visible on an X-ray. As PsA advances, however, an X-ray will show the bones that experience damage and shape changes.

As PsA progresses, bone changes may be visible by looking, for example, at the hands or feet.

If someone has a history of psoriasis and symptoms that could indicate PsA, but an X-ray reveals no changes, a doctor may recommend other forms of imaging to investigate further.

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X-ray showing a pencil-in-cup deformity due to psoriatic arthritis.
Image credit: Leung, Ying Ying & Tam, Lai-Shan & W KUN, Emily & Li, Edmund. (2008). Psoriatic Arthritis: an update on classification, clinical feature and therapies. Hong Kong Bulletin of Rheumatic Diseases. 8. 1-11.

Procedure

A radiographer will:

  1. Ask the person to sit, lie down, or stand according to the image they need.
  2. Prepare the person’s position and ask them not to move.
  3. Leave the room to take the images.
  4. Return and let the person know when they finish.

An X-ray usually takes only a few minutes.

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MRI image showing changes due to psoriatic arthritis, including bone loss and excess synovial fluid in and around the knee joint.
Image credit: Mathew, A. J., & Østergaard, M. (2020). Magnetic Resonance Imaging of Enthesitis in Spondyloarthritis, Including Psoriatic Arthritis-Status and Recent Advances. Frontiers in medicine, 7, 296

An MRI scan can provide a detailed image of soft and hard tissues. It is less common in PsA diagnosis than an X-ray, but it can detect early soft tissue inflammation that is present before bone and joint damage occur.

It can show inflammatory changes in:

  • joints
  • tendons
  • entheses, which attach the tendons and ligaments to the bone
  • the spine

A doctor may use an MRI to check for problems with the tendons and ligaments, especially in the lower back and feet.

An MRI scan is more likely than an X-ray to detect early signs of PsA, but an MRI alone cannot confirm a diagnosis. A doctor will also need to consider other factors and symptoms, such as a history of psoriasis or the presence of dactylitis.

One reason for this is that rheumatoid arthritis (RA) can show up similarly on an MRI.

Procedure

The radiographer will most likely:

  • Ask the person to remove any jewelry or metallic items and check if they have a pacemaker or other implanted device.
  • Ask them to lie down on a bed and give them some earplugs or headphones.
  • Move the bed inside a “donut” shaped machine.
  • Instruct the person to lie as still as possible during the scan.
  • Leave the room to carry out the scan, but communicate with the person through the headphones during the procedure.

An MRI scan usually lasts 15–90 minutes, depending on what the investigation is for.

Does Medicare cover an MRI scan?

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Ultrasound scan showing enthesitis due to psoriatic arthritis.
Smerilli, G., Di Matteo, A., Cipolletta, E., Grassi, W., & Filippucci, E. (2021). Enthesitis in Psoriatic Arthritis, the Sonographic Perspective. Current rheumatology reports, 23(9), 75

Like an MRI, an ultrasound scan can detect joint inflammation and damage, as well as soft tissue changes. It may show signs of PsA even before a person notices symptoms. This can lead to early detection in people who already have skin psoriasis.

A doctor may also recommend it for someone who does not have a psoriasis rash but might have psoriatic arthritis.

Ultrasound can show signs of inflammation, such as:

  • blood vessel changes
  • soft tissue thickening under the skin
  • form changes around the nail that could indicate nail psoriasis or the early signs of PsA

A doctor may use a Doppler ultrasound to test for changes around the nail. This is a special type of ultrasound for assessing blood flow.

Procedure

In an ultrasound, a radiologist will:

  • Ask the person to remove any clothing from the area to be assessed.
  • Ask them to sit or lie down comfortably.
  • Apply a gel over the area for examination.
  • Pass a small device over the area and move it over the skin to collect images.

The gel may feel cold, but the procedure is usually painless. However, if the radiographer needs to press into a joint of a person with PsA, it may be slightly tender.

What are the differences between PsA and RA?

PsA shares some signs and symptoms with RA, reactive arthritis, and gout. They all involve joint pain, swelling, and a sensation of warmth in the affected areas.

Before diagnosing PsA, doctors need to rule out other forms of arthritis as the cause of joint pain and swelling.

To do this, they will likely:

  • ask about symptoms
  • review the person’s individual and family medical history, and order some tests
  • examine the skin, joints, nails, and eyes
  • order blood tests to check for inflammation markers and antibodies and rule out other possible causes
  • do a skin biopsy to test for psoriasis

How do doctors diagnose PsA, and what criteria do they use?

A doctor may recommend a test if a person has symptoms that could indicate PsA, such as:

  • joint pain and swelling
  • an inflammation of the eyes known as uveitis
  • nail and skin changes that can occur with psoriasis
  • a history of psoriasis

PsA can occur at any age, but it commonly appears between the ages of 30 and 50 years. A person with skin or nail psoriasis often has a significantly higher chance of developing PsA.

What is the link between psoriasis and PsA?

Doctors consider PsA an aggressive disease that can affect people’s overall health and quality of life. However, some drugs can help manage symptoms, slow the progression of the disease, or both.

A doctor may prescribe:

Current guidelines also recommend avoiding or quitting smoking, managing weight, and getting regular exercise.

With treatment, some people have complete relief from symptoms, but others continue to experience inflammation. A person with PsA will need ongoing treatment to manage the disease and reduce the risk of complications, such as eye problems, joint damage, and reduced mobility.

People with PsA are also likely to experience obesity, type 2 diabetes, and other aspects of metabolic syndrome more often. A doctor can advise on measures to reduce the risk of these complications.

Which medications can help manage PsA?

PsA is a type of arthritis that often occurs in people with psoriasis.

To diagnose PsA, a doctor will usually consider the person’s symptoms and medical history, carry out some blood tests and order some imaging tests, such as an X-ray, MRI, or ultrasound.

An X-ray can reveal damage in bones and joints, while an MRI or ultrasound can show soft tissue damage, which may be present at an earlier stage.

None of these tests alone can diagnose PsA, but a doctor will use different tests in combination to rule out other conditions and narrow down the options.

An early diagnosis and prompt treatment may improve the outlook for a person with PsA.