Radiology, such as X-ray imaging, can help doctors detect specific structural changes to your joints that may indicate psoriatic arthritis (PsA). They may also use other imaging, such as MRI, to detect inflammation.

Imaging, including radiology, plays an important role in allowing doctors to diagnose PsA and distinguish it from other joint conditions. It can also help doctors see the extent of your joint damage and track how the disease progresses.

Doctors often use X-rays as the first type of imaging to diagnose PsA, but you may also receive:

  • ultrasound
  • MRI
  • CT scans

This article examines the role that imaging plays in diagnosing and tracking PsA.

Peripheral vs. axial PsA

Doctors often classify PsA as peripheral or axial depending on which joints the condition affects.

Peripheral disease affects the joints in your extremities, like your hands or feet. Axial disease affects your spinal cord. Some people have both types.

Peripheral PsA is more common, but 25–70% of people also have spinal cord involvement.

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X-ray image of hands with showing signs of psoriatic arthritisShare on Pinterest
Hand X-rays can show signs of psoriatic arthritis, such as bone erosion and the “pencil-in-cup” deformity.
Copyright © 2015 The Korean Dermatological Association and The Korean Society for Investigative Dermatology CC BY-NC 3.0

X-rays are the most performed imaging technique for PsA. They create an image of your joints by passing a small amount of radiation through your body.

Around one-quarter of people with early PsA have joint damage that shows up on X-rays, and about half of people have visible damage within 2 years, according to a notable 2003 study.

X-rays are advantageous because they’re:

  • fast
  • relatively inexpensive
  • reliable
  • widely available

Doctors can use X-rays to identify structural damage to your joints, such as:

X-rays require exposure to a small amount of radiation. For this reason, doctors may prefer MRI for spinal cord evaluation in children and young adults.

Axial PsA

Changes to your spine visible on an X-ray include:

  • new bone formation
  • changes to multiple levels of your spine
  • joint changes on one side, which highly suggests PsA
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CT scans can help doctors detect signs of psoriatic arthritis like bone erosion and structural changes, especially in areas like the shoulder, spine, or pelvis.
Crespo-Rodríguez, A.M., Sanz Sanz, J., Freites, D. et al. Role of diagnostic imaging in psoriatic arthritis: how, when, and why. Insights Imaging 12. CC BY 4.0

A CT scan is a series of X-rays that produces a 3D image of your joint.

CT scans are great for seeing:

  • bone erosions
  • new bone formation
  • joint space changes

The role of CT scans in diagnosing PsA is usually limited to people who can’t receive MRI. This is because CT scans can’t detect active inflammation and require exposure to higher amounts of radiation than plain X-rays.

CT scans might be helpful in complex and difficult joints such as the:

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A knee MRI shows changes due to psoriatic arthritis, such as the buildup of synovial fluid around the joint.
Copyright © 2020 Mathew and Østergaard. CC BY

MRI uses powerful magnets to create an image of the inside of your body. MRI is highly sensitive for detecting inflammation in and around your joints and in your soft tissues.

MRI is more sensitive than X-ray for detecting early joint inflammation and damage.

Doctors often recommend MRI for sacroiliitis if X-rays are inconclusive. Sacroiliitis is a potential feature of PsA when the SI joint becomes inflamed.

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Ultrasound images can reveal areas of bone damage as well as inflammation due to psoriatic arthritis.
Smerilli G, Di Matteo A, Cipolletta E, Grassi W, Filippucci E. Enthesitis in Psoriatic Arthritis, the Sonographic Perspective. Curr Rheumatol Rep. 202 CC BY 4.0 DEED

Ultrasound uses high frequency sound waves to create an image of your tissues. Ultrasound is:

  • quick
  • cheap
  • widely available

Ultrasound also allows doctors to scan multiple sites in one session. Like MRI, ultrasound is more sensitive than plain X-ray for detecting early joint inflammation. Ultrasound is a useful technique for evaluating inflammatory changes in soft tissues such as:

  • joint lining
  • tendons
  • bursas
  • entheses, where tendons or ligaments connect to bone

The main drawbacks of ultrasound are that it can’t penetrate bone and it doesn’t help doctors identify changes to your spinal cord well.

When might a doctor recommend radiologic tests for psoriatic arthritis?

Imaging plays a vital role in the early diagnosis of PsA. Your doctor may send you for imaging if you have characteristic features such as:

  • joint pain and swelling
  • nail and skin changes
  • a personal or family history of psoriasis
  • uveitis, inflammation of the middle layer of your eye
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Doctors can use imaging to look for characteristic signs of PsA to help distinguish it from other types of inflammatory arthritis.

For example, seeing the “ray pattern,” when all three joints in one finger or toe are inflamed, can help doctors differentiate PsA from rheumatoid arthritis.

Another characteristic sign of PsA is the pencil-in-cup deformity. This happens when a bone in your finger is narrow and the bone below it is wide.

Doctors can usually diagnose PsA if you have classic symptoms of psoriasis and inflammatory arthritis in a typical PsA pattern.

Other tests you may receive to support your diagnosis include:

After imaging, your doctor may recommend medications to help manage your symptoms, such as:

They may also recommend making an effort to incorporate certain lifestyle changes, such as:

X-rays are the most common type of imaging doctors use to diagnose and monitor PsA. Doctors also use other types of imaging such as CT scans, ultrasound, or MRI.

Your doctor might recommend further imaging if initial X-rays are inconclusive. Other scans, such as MRI or ultrasound, can better show inflammation in your soft tissues.

Your doctor may recommend MRI instead of X-rays as your initial scan if they want to limit your radiation exposure.