A PsA diagnosis is a complex process, and it will probably take more time than a single doctor visit. The diagnosis is made through a variety of methods.

Psoriatic arthritis (PsA) is a type of arthritis that develops in about 30% of people who have psoriasis.

Psoriatic arthritis can develop suddenly or slowly over time.

In about 80% of cases, PsA develops after psoriasis is diagnosed. PsA primarily affects joints, which can be in any part of your body. The main symptoms include:

  • fatigue
  • joint pain, swelling, and stiffness
  • reduced range of motion

If you’re experiencing joint stiffness, pain, or swelling that persists, be sure to see a medical professional for a diagnosis.

Read on to learn how a diagnosis of psoriatic arthritis is made.

Read on to learn how PsA is diagnosed.

Symptoms and family history

PsA is known to have a strong genetic connection. One 2020 study showed that about 40 percent of people with psoriasis or PsA had a family member with either psoriasis or PsA.

In the study, those with a family history of PsA had a higher risk for developing deformities from PsA, but a lower risk for developing plaque psoriasis, the red, scaly skin patches that are a common symptom of psoriasis.

Researchers are only now beginning to decipher the specific genes associated with PsA. The main challenge is distinguishing genes responsible for psoriasis from those responsible for PsA.

Identifying the genes that lead to PsA may pave the way toward developing gene therapy for treating PsA.

CASPAR criteria for diagnosis

Diagnosing psoriatic arthritis relies on markers in an established system called the Classification Criteria for Psoriatic Arthritis (CASPAR).

The criteria are each assigned a point value. Each one has a value of 1 point except for current psoriasis, which has a value of 2 points.

The criteria are as follows:

  • current psoriasis outbreak
  • personal or family history of psoriasis
  • swollen fingers or toes, known as dactylitis
  • nail problems, like separation from the nail bed
  • bone growths near a joint that are visible on an X-ray
  • absence of rheumatoid factor (RF)

A person must have at least 3 points based on the CASPAR criteria to be diagnosed with psoriatic arthritis.

Repeated flare-ups

People with PsA usually experience periods of increased disease activity called flare-ups. Symptoms of a flare-up include muscle and joint pain, and swelling. You may also have tendonitis and bursitis.

In psoriatic arthritis, fingers and toes may swell up. This is called dactylitis. You may also experience pain and swelling in your wrists, knees, ankles, or lower back.

Repeated flare-ups will be one indicator for a PsA diagnosis. Sometimes, psoriasis flare-ups will coincide with a psoriatic arthritis flare-ups.

Common triggers for psoriatic arthritis flare-ups include:

  • exposure to cigarette smoke
  • infections or skin wounds
  • severe stress
  • cold weather
  • alcohol misuse
  • taking certain medications and foods

Psoriatic arthritis can’t be diagnosed with any single test. Your doctor will probably order a number of tests and examine all of the evidence to make a diagnosis.

Your doctor will not only be looking for indications of PsA in your test results. They will also be looking for results that rule out other conditions as well as results that eliminate the possibility of PsA.

For example:

  • Blood tests can help rule out gout and rheumatoid arthritis (RA).
  • A blood test that shows mild anemia points toward the possibility of PsA (and can also point toward RA).
  • Presence of RH factor in your blood means you don’t have PsA.

Imaging tests for psoriatic arthritis

Imaging tests can help your doctor closely examine your bones and joints. Some of the imaging tests your doctor may use include:

  • X rays. X-rays aren’t always useful in diagnosing early stage psoriatic arthritis. As the disease progresses, your doctor may use imaging tests to see changes in the joints that are characteristic of this type of arthritis.
  • MRI scans. An MRI alone can’t diagnose psoriatic arthritis, but it may help detect problems with your tendons and ligaments, or sacroiliac joints.
  • CT scans. These are used primarily to examine joints that are deep in the body and not easily seen on x-rays, such as in the spine and pelvis.
  • Ultrasounds. These tests can help determine the progression of joint involvement and pinpoint the location.

Blood tests for psoriatic arthritis

Blood tests in themselves will not confirm a PsA diagnosis. These tests are usually given to determine the presence of inflammation and to rule out other conditions.

Read on to learn what types of blood tests may be given to make a PsA diagnosis.

  • Erythrocyte sedimentation rate (ESR, also called sed rate). This gauges your body’s degree of inflammation, though not specifically for PsA. It measures the amount of red blood cells that settle in a vial of blood, which is greater when you have inflammation.
  • C-Reactive protein (CRP). Your doctor may order this test to check for an elevated C-reactive protein (CRP) level. This test is not specific for PsA, but it does indicate the presence of inflammation.
  • Rheumatoid Factor (RF). Presence of this antibody in your blood indicates rheumatoid arthritis (RA). Its presence means you don’t have PsA.
  • Anti-Cyclic Citrullinated Peptide test. These antibodies usually indicate RA. However, their presence can occur in other forms of arthritis, and your doctor will probably test for them.
  • Human leukocyte antigen B27 (HLA-B27). This is a protein found on the surface of white blood cells in some people with PsA.
  • Serum uric acid. Your doctor may take a sample of fluid from your joints to check for uric acid crystals. Elevated uric acid in the blood or crystals in bodily fluids indicate gout.

Bone density scan

In a bone density scan, X-rays are used to measure the density of calcium and other minerals in a particular portion of your bones. The higher the density, the stronger and more healthy your bones are.

PsA is associated with low bone density. Therefore, this test indicates possible osteoporosis and risk of fracture, which can be managed to lower the risk of fracture.

Like other tests for PsA, a bone density scan does not provide the basis for a definitive diagnosis. Low bone density can also result from other conditions and from the use of certain medications called corticosteroids.

Iron deficiency

Chronic inflammation associated with PsA can cause anemia, or a reduction of your healthy red blood cells.

A low hemoglobin, or red blood cell count, can be another indication of PsA. Low hemoglobin can also result from iron deficiency.

Once you’ve been diagnosed, your treatment plan will depend on the severity of your symptoms. Read on to learn about the various treatments for PsA.


For joints that are painful but not yet at risk of being damaged, over-the-counter (OTC) nonsteroidal anti-inflammatory drugs (NSAIDs) may be recommended.

These include ibuprofen (Motrin or Advil) and naproxen (Aleve). More severe pain might require a prescription anti-inflammatory pain reliever.


Disease-modifying antirheumatic drugs (DMARDs) can help prevent PsA from damaging joints. Examples of DMARDs include methotrexate and sulfasalazine.

These drugs might help to slow disease progression if you’re diagnosed in the early stages of psoriatic arthritis.


If you’re diagnosed after you’ve had psoriatic arthritis for some time, this will affect your treatment decisions.

Your doctor may prescribe an immunosuppressant to prevent flare-ups and keep your joints from being damaged further.


Biologics such as TNF-alpha or IL-17 inhibitors are another treatment that reduces pain. However, they come with some safety concerns such as suppression of the immune system and increased risk of infection.

Enzyme inhibitors

Enzyme inhibitors block an enzyme called Phosphodiesterase-4 (PDE-4), which can slow the development of inflammation.

They can cause side effects, which may include:

  • diarrhea
  • nausea
  • headache
  • mood disturbance


Joint inflammation that is severe is often addressed with a steroid injection at the site of the affected joint to help decrease pain and inflammation.

If the joint is seriously damaged or destroyed, you might require joint replacement surgery.

Light therapy

Various forms of light therapy are used to treat psoriasis, usually in small focused areas. It’s hoped that this will prevent or slow psoriasis leading to PsA.

Some forms of light therapy include:

  • sunlight
  • narrowband UVB phototherapy
  • excimer laser


PsA seldom advances to the stage where you need surgery. But if no other treatment gives relief and your movement is seriously restricted, surgery may be recommended.

Surgery is an option that may relieve pain or help a joint to work again. Surgical options might include:

  • Synovectomy. This procedure removes the synovial tissue, or lining, of particular joints such as the shoulder, elbow, or knee. It is done when medication does not provide relief.
  • Joint replacement (arthroplasty). This is surgery to replace a particular painful joint with an artificial joint, or prosthetic.
  • Joint fusion (arthrodesis). This procedure fuses two bones to make a joint stronger and less painful.

Since there is no single test for psoriatic arthritis, a definitive diagnosis may take time. If you have psoriasis and joint pains, your doctor or dermatologist may refer you to a rheumatologist.

A rheumatologist is a doctor who specializes in diagnosing and treating arthritis and autoimmune disease.

Be prepared to list all your symptoms, give a complete medical history, and tell your doctor if you’ve been diagnosed with psoriasis.

Your rheumatologist will conduct a physical exam. They may also ask you to perform simple tasks that demonstrate your range of motion.

Diagnosing psoriatic arthritis can be like solving a mystery. Your rheumatologist may perform tests to rule out other forms of arthritis, including gout, RA, and reactive arthritis.

They may look for an elevated ESR or CRP level, which indicates some amount of inflammation. Your rheumatologist may also order various imaging tests to look for joint damage.

Medications and surgery aren’t the only treatment options for psoriatic arthritis. There are lifestyle choices that can make your condition more tolerable.

These include changes in diet, specifically adding in more omega-3s, and adopting a safe exercise regimen.

Other lifestyle choices that may help include:

  • maintaining a healthy-for-you weight
  • taking steps to protect your joints
  • avoiding your flare-up triggers

Psoriatic arthritis, when treated, can usually be slowed down to prevent further joint damage.