Psoriatic arthritis and ankylosing spondylitis are two types of spondyloarthritis. They can cause swelling, stiffness, and pain in the joints.

Psoriatic arthritis (PsA) usually occurs in people with psoriasis, an autoimmune condition that causes cells to develop rapidly, leading to various skin symptoms.

Ankylosing spondylitis (AS) is a type of arthritis that mainly affects the spine and lower back, though the effects can extend throughout the body over time.

Below, we explore the differences between PsA and AS, including their symptoms and treatments and how doctors diagnose them.

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Psoriatic arthritis (PsA) is a type of chronic inflammation that occurs in up to 1 in 5 people with psoriasis. PsA often begins when people are between 30 and 50 years old, but it can emerge at any age.

The condition can affect a variety of joints, including those in the arms, legs, and spine.

Learn more about how PsA affects the body here.


PsA has five major subtypes:

  • Distal interphalangeal predominant: This affects the joints in the tips of the fingers and toes.
  • Symmetrical polyarthritis: This affects multiple small joints in the hands or feet.
  • Asymmetrical oligoarthritis and monoarthritis: This affects only one or a few finger and toe joints.
  • Predominant spondylitis: This mainly affects bones in the spine.
  • Arthritis mutilans: This is severe and can cause deformity of the hands, feet, and spine. It is the most significant cause of functional disability among people with PsA.

PsA is similar to rheumatoid arthritis and, until 1964, the two were considered the same condition. But unlike rheumatoid arthritis, PsA does not create rheumatoid factors in the blood.

AS is a different type of spondyloarthritis.

It causes severe, chronic pain and inflammation in and around the spine and the sacroiliac joints, which connect the pelvis to the spine. In some cases, the condition causes spinal vertebrae and the sacroiliac joints to fuse together. AS may also affect other joints in the body.

AS is very complex, and it can be challenging to identify the cause. Research shows that there is a strong genetic component, but low vitamin D levels could also contribute to the development of the condition.

Learn more about the effects of AS on a person’s body here.

Symptoms of PsA are mild and slow to develop in some people, and sudden and severe in others.

Common symptoms include:

  • swelling of the fingers and toes, sometimes called “sausage fingers”
  • pain, swelling, and tenderness in the joints and tendons
  • stiffness and a reduced range of motion
  • fatigue
  • pitting and other changes to nails
  • changes to the eyes, including uveitis and conjunctivitis

Many people with psoriasis have the condition for at least 10 years before PsA begins to develop. Less commonly, people develop PsA before having noticeable symptoms of psoriasis.

The severity of AS symptoms and the speed at which they arise can vary, as with PsA.

Initially, a person with AS may experience a loss of appetite and possibly a fever. Pain and stiffness in the early stages often begin in the buttocks and lower back.

As the condition progresses, the pain spreads through the spine and into the neck. Tenderness may also develop in the hips, thighs, heels, ribs, and shoulder blades.

The effort of managing the inflammation within the body can cause fatigue. Also, the inflammation can lead to anemia. Bowel inflammation and eye conditions, including uveitis, are also associated.

Less often, AS symptoms begin beyond the spine in a peripheral joint, such as the ankle, shoulder, or hip.

When this happens, it can result from enthesitis — inflammation where a tendon or ligament connects to bone. When symptoms are only present in peripheral joints, AS can be more challenging to diagnose.

There is no single test that a doctor can use to check for PsA or AS. Instead, they must use a combination of the following techniques:

  • evaluating personal and family medical histories
  • doing a physical examination
  • considering the results of laboratory tests, such as a blood test for the HLA-B27 gene
  • X-rays
  • MRI scans

For AS, the deciding factor is often the condition of the sacroiliac joints. However, AS may not affect the area until the condition has been present for 10 years, so other tests are necessary.

There is currently no cure for either PsA or AS. However, there are various ways to reduce the symptoms, maximize flexibility, maintain posture, and limit complications. Effective treatments also slow down the progression of both conditions.

Treatment options for AS are mostly drug-related and surgical, but they can also include:

Individual treatment plans vary slightly, depending on the person and the severity of the condition.


The following types of drugs may benefit people with spondyloarthritis, a type of disease that includes PsA and AS:

A 2019 study suggests that NSAIDs and TNF inhibitors are the leading classes of medication for these conditions.


People with severe PsA or AS may need to undergo surgery. Hip joint replacement is a common surgical procedure for people with spondyloarthritis.

If a person has a severely downward-curving spine, posture correction surgery can help, though the risks of this type of procedure are high.

Treatment options continue to evolve as researchers investigate new therapies.

PsA and AS are two types of spondyloarthritis. They cause chronic swelling, pain, and tenderness in and around the joints.

Both PsA and AS can be challenging to diagnose, and neither condition is currently curable. However, therapies can ease symptoms and improve the quality of life. Research into new treatment options is ongoing.