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Diagnosing psoriatic arthritis (PsA) as early as possible is an important step in treating this progressive autoimmune disease.

An X-ray is just one diagnostic tool that can help doctors look for changes in the joints and bones.

In this article, we take a look at what a psoriatic arthritis X-ray might show, what the procedure is like, and other diagnostic tools used to confirm PsA.

PsA may affect joints big and small. Some people experience symptoms in a few joints, while the condition may be more widespread in others.

Overall, PsA primarily affects joints in the:

  • fingers
  • wrists
  • knees
  • ankles
  • toes

Sometimes, PsA may also develop in the back and hips. PsA with spinal involvement is also known as psoriatic spondylitis.

Your doctor may order X-rays specifically for areas of the body where you’re experiencing symptoms. These include redness, inflammation, and pain that may be interfering with your daily activities.

Unlike other imaging tests, X-rays are suitable for capturing quick images of various parts of the body. During the procedure, electromagnetic radiation is used to help capture 2-D pictures of bones, joints, and organs before they’re sent to a computer for evaluation.

When your doctor receives the images, they will look for noticeable signs of damage that could be due to arthritis, such as:

  • damage to soft tissues
  • decreased cartilage
  • smaller spaces where joints ought to be
  • bone spurs
  • bone erosion

What psoriatic arthritis X-rays look like

Here are some examples of X-ray images showing different parts of the body affected by PsA.

While X-rays are important to help determine damage by arthritis, such imaging tests can’t confirm PsA alone. Part of this is due to the fact that other types of arthritis, such as rheumatoid arthritis (RA), may look similar on X-rays.

To distinguish PsA from other autoimmune conditions that affect the joints, your doctor will need to run other exams and tests to provide an accurate diagnosis. These include:

A thorough medical history

Your personal medical history is an important factor to consider when diagnosing PsA. Your doctor will ask questions about your symptoms, including their severity and when you first noticed them.

Additionally, your doctor will ask about any personal or family history of psoriasis, PsA, and other autoimmune conditions. Psoriasis may increase your chances of developing PsA, and both conditions can run in families.

Having a family history of autoimmune diseases may also increase your personal risk of developing PsA — even if your parents or relatives have other types of autoimmune conditions.

Physical exam

During a physical exam, your doctor will inspect areas of the body that PsA commonly affects. They will look for signs, such as:

  • redness
  • heat
  • swelling
  • tenderness

They may also ask you to perform range-of-motion exercises to assess joint function.

About one-third of people with psoriasis develop PsA. Thus, your doctor may also evaluate skin symptoms related to psoriasis, including skin patches that are:

  • red, especially around the borders of the rash
  • silver-colored on top, due to dead skin cell buildup
  • extremely itchy
  • possibly painful
  • located around the scalp, knees, and elbows

Psoriasis may also affect your nails, causing them to:

  • develop white spots
  • crack
  • pit
  • lift from the nail bed

Blood testing

While there’s not a single blood test that can diagnose PsA alone, certain markers could help confirm this disease. Your doctor will specifically look for the presence of c-reactive protein (CRP) and rheumatoid factor (RF) in the blood.

A CRP range can be anywhere from 0.8 to 100 mg/dL. While any CRP above 0.3 mg/dL is above normal, CRPs between 1.0 and 10.0 mg/dL are seen in autoimmune diseases like PsA. Much higher levels are associated with viral and bacterial infections.

RF is another indicator of certain autoimmune diseases, particularly rheumatoid arthritis (RA). Based on this information, other test results, and the presence of psoriasis, your doctor may diagnose you with PsA instead.

It’s important to note, however, that a negative RF doesn’t rule out RA. A person may be diagnosed with seronegative RA and have symptoms of inflammatory joint disease similar to RF, even if their RF is negative.

Other possible types of blood tests used to detect PsA or rule out other autoimmune diseases include:

  • genetic testing
  • citrullinated peptide antibodies, which also occur in RA and not PsA
  • anti-nuclear antibodies, which may be found in all types of autoimmune conditions

Other imaging tests

While X-rays are standard in taking images of bones and joints, these may not be the only imaging tests used to diagnose PsA.

For example, an ultrasound test can also provide some of the same information as a traditional X-ray might, including images of soft tissues, bone spurs, and bone erosion.

However, an ultrasound may be more beneficial in early stages of PsA, where some of these signs may get missed on an X-ray.

Magnetic resonance imaging (MRI) or computed tomography (CT) scans may also be considered as a way to find more detailed signs of inflammation in soft tissues around the bones.

During the X-ray procedure, your doctor or a technician will place the part of your body being examined beneath or in front of an X-ray machine. When they turn on the machine, the X-rays travel through the targeted part of the body to produce images within minutes.

Bone and joints will appear white in color against a black background. Surrounding tissues and organs will appear gray.

While X-rays may be a necessary step in diagnosing PsA, it’s important to discuss any concerns with radiation exposure, particularly in children. Your doctor will order X-rays only when needed to decrease any risk from the small amounts of radiation used.

X-rays can help identify inflammatory damage to your joints and bones, but these aren’t the only tools your doctor will use to help diagnose PsA.

Aside from psoriasis, many of the clinical signs of PsA are similar to RA, so it’s important that your doctor also conduct a thorough physical exam, medical history, blood testing, and additional imaging tests as appropriate.