Psoriatic Arthritis vs. Rheumatoid Arthritis: What’s the Difference?

All forms of arthritis involve tenderness and swelling of the joints. And, at first glance, psoriatic arthritis (PsA) can be very hard to differentiate from other common types of arthritis, including rheumatoid arthritis (RA) and osteoarthritis (OA).

Because psoriatic arthritis symptoms can overlap with those of rheumatoid arthritis and osteoarthritis — not just swollen, achy joints but also stiffness (especially in the morning) and chronic fatigue — diagnosing this autoimmune disease can be tricky.

“Unlike rheumatoid arthritis, there is no blood test that can determine if a person has psoriatic arthritis,” says M. Elaine Husni, MD, MPH, a rheumatologist at the Cleveland Clinic in Ohio.

Psoriatic arthritis can also affect the body in different ways depending on the person and how advanced the disease is, says Dr. Husni. As a result, a rheumatologist may need to examine a patient several times and run a number of tests before having enough information to make a definitive diagnosis.

One unique symptom of psoriatic arthritis that doctors look for is the presence of psoriasis, a condition that causes thick, discolored, scaly skin patches known as plaques, as well as pitted nails or nails that separate from the nail bed, according to the American Academy of Dermatology.

Like psoriatic arthritis, psoriasis stems from a faulty immune response, in which the immune system mistakenly attacks healthy cells and tissues.

About a third of people with psoriasis develop psoriatic arthritis, according to the Arthritis Foundation. “About 10 percent of people develop arthritis first, then psoriasis later,” says Eric Ruderman, MD, a rheumatologist at Northwestern Medicine in Chicago.

RELATED: Is It Psoriatic Arthritis or Is It Gout?

Because psoriatic arthritis impacts the skin as well as the joints, it’s sometimes referred to as a “double whammy,” or “like rheumatoid arthritis but with a nasty skin rash,” according to the arthritis advocacy group CreakyJoints.

Both psoriatic and rheumatoid arthritis are autoimmune disorders that cause joint inflammation, pain, and stiffness, as well as chronic fatigue. But there are differences in how the diseases develop and affect the joints.

According to Kathleen Maksimowicz-Mckinnon, DO, a rheumatologist at MUSC Health in Charleston, South Carolina, there are some telltale signs that your arthritis pain is due to psoriatic arthritis, and not rheumatoid arthritis. These include:

• Different joints hurt on different sides. Psoriatic arthritis typically affects joints asymmetrically. Rheumatoid arthritis, on the other hand, tends to impact joints in matching pairs on opposite sides of the body (such as both wrists).
• You have lower back pain. Psoriatic arthritis often involves inflammation of the lower spine, whereas rheumatoid arthritis rarely affects the spine.
• The joints closest to your nails are sore. Psoriatic arthritis often affects the distal joints, which are at the tip of the finger near where the nail starts. With rheumatoid arthritis, the joints that connect your fingers to your hands (the metacarpophalangeal joints) are more commonly impacted.
• You have foot or elbow pain. Psoriatic arthritis can cause inflammation or pain at the point where tendons attach to bones, called enthesitis. “This can hurt more than the joints themselves,” says Dr. Ruderman. Enthesitis most commonly occurs at the heel, on the bottom of the foot, or in the elbow.

Joint pain and stiffness, especially in the morning or after resting, can be a symptom of either psoriatic arthritis or osteoarthritis — the most common type of arthritis.

Unlike autoimmune forms of arthritis, osteoarthritis is the result of wear-and-tear damage to cartilage — the slippery covering that allows bones to easily slide over each other when joints bend, says the Arthritis Foundation.

Damage to the cartilage can result in bone grinding directly on bone, which causes pain and restricts movement.

Osteoarthritis primarily affects the hands, knees, hips, and spine, and can create a grating sensation, along with popping or crackling, when you use the joint, says the Mayo Clinic. You may also notice hard lumps of bone near the joint, or the joint may look distorted.

While psoriatic arthritis symptoms tend to flare and subside, osteoarthritis-related pain and swelling usually become progressively worse over time.

Diagnosing psoriatic arthritis is typically a multistep process. In addition to a physical exam and a comprehensive medical history, your doctor may order a number of tests.

The different ways that psoriatic arthritis and rheumatoid arthritis impact the joints and tendons are often subtle and may not be detected in a physical exam but can be identified in imaging tests such as X-rays or ultrasound.

Blood tests also help doctors differentiate psoriatic arthritis from rheumatoid arthritis. Although there is no blood test for psoriatic arthritis, doctors can look for the presence of two antibodies — rheumatoid factor (RF) and anticyclic citrullinated peptide (anti-CCP) — that suggest a rheumatoid arthritis diagnosis, according to the Arthritis Foundation.

RELATED: Psoriatic Arthritis Diagnosis Could Take More Than 2 Years, Study Shows

The main goals of all arthritis treatment are to reduce symptoms and improve quality of life. Methods vary depending on the type of arthritis.

“Rheumatoid arthritis can be very destructive if it’s not treated, which is why we treat it aggressively with biologics,” says Ruderman. “But psoriatic arthritis doesn’t manifest that way. Fewer than half of people with psoriatic arthritis develop a particularly aggressive form, which makes treatment challenging because we don’t want to overtreat it.”

Even so, the pain and discomfort associated with psoriatic arthritis can be significant. A study found that the overall pain, joint pain, and fatigue reported by psoriatic arthritis patients were significantly greater than that reported by people with rheumatoid arthritis.

Unless someone has an existing condition, such as elevated blood pressure or kidney disease, nonsteroidal anti-inflammatory drugs (NSAIDs) are recommended for joint symptoms in milder forms of psoriatic arthritis, says Husni.

Topical creams, ointments, and lotions are often used to address the scaly, itchy skin rashes that occur with psoriasis.

If there are signs of joint damage, doctors treat psoriatic arthritis more aggressively with medications like the ones used to treat rheumatoid arthritis, says Ruderman. These include disease-modifying anti-rheumatic drugs (DMARDs) and biologics.

“Without disease-modifying therapy, the prognosis for psoriatic arthritis and rheumatoid arthritis is usually significantly worse than for osteoarthritis,” says Neil Kramer, MD, a rheumatologist with the Atlantic Medical Group in Summit, New Jersey.

As with rheumatoid arthritis, psoriatic arthritis complications can include increased risk of heart disease, depression, obesity, certain cancers (such as non-Hodgkin lymphoma), infections, and osteoporosis. In addition, “People with psoriasis or psoriatic arthritis have a high incidence of metabolic syndrome, fatty liver disease, and cholesterol abnormalities,” says Ruderman.

“We need to think of it as psoriatic disease that affects the joints, tendons, skin, and nails, and use multiple things to treat it,” he adds.

Additional reporting by Becky Upham.