Psoriatic arthritis (PsA) and osteoarthritis (OA) are two types of arthritis. Both affect the joints and produce symptoms such as stiffness, swelling, and pain. However, PsA is primarily an inflammatory autoimmune condition (like rheumatoid arthritis), whereas OA is a degenerative disease, caused by mechanical wear on joints themselves.

Because of the similarities between PsA and OA — and because the results of imaging and blood tests are not always clear — the diagnostic process can be a challenge. Some people living with one type may even be misdiagnosed with the other, like one MyPsoriasisTeam member who wrote, “It turned out that I didn’t have osteoarthritis, but psoriatic arthritis was the culprit.”

These types of scenarios can cause confusion when it comes to finding an effective treatment.

Here’s what people need to know about osteoarthritis versus psoriatic arthritis, including the key differences and similarities between their symptoms, causes, diagnosis, and treatments.

6 Differences Between Psoriatic Arthritis and Osteoarthritis

There are several important differences between psoriatic arthritis and osteoarthritis.

1. Osteoarthritis and Psoriatic Arthritis Are Distinct Conditions

PsA occurs when the immune system mistakenly attacks the body’s own healthy tissues instead of foreign invaders, like viruses and bacteria. PsA is related to psoriasis, an autoimmune disease distinguished by scaly patches on the skin that can burn or itch.

Osteoarthritis is a condition in which cartilage — the cushiony layer between the joints — wears away over time. Bones begin to rub against each other, causing pain, crunching or grinding, and joint damage. Mild inflammation may occur in OA, but this is not characteristic of the condition and does not come from immune system issues.

2. Patterns of Joint Pain Differ

Pain from PsA tends to come and go, flaring up and then settling down as inflammation waxes and wanes. OA pain usually comes on slowly over the course of years. As the cartilage wears down, it becomes more painful to use that joint.

Although people with both types of arthritis will feel stiff, the patterns differ. Those with PsA tend to experience more extreme stiffness that affects several areas of the body. These bouts are more intense in the morning, lasting more than 30 minutes — and sometimes, even hours. Stiffness usually can become less intense or disappear with movement and as the day goes on.

People with OA may wake up with specific joints that are stiff or experience bouts throughout the day (but the stiffness usually goes away within about 30 minutes). Pain, however, can become more intense with movement.

Stiffness in OA, in particular, tends to be tied to overuse of the joints. When a person with OA uses a joint, it hurts. If they use it too much, the joint may become swollen and painful, although those symptoms should ease with rest. For people with PsA, use may make a stiff joint feel better and usually won’t worsen symptoms. Ultimately, joint use is not tied to pain and swelling in PsA as it is with OA.

People with either PsA or OA may develop bony growths called bone spurs in their joints over time. A doctor can differentiate them by their location or aspect (appearance and characteristics) seen on X-rays. For example, nodules of finger are rare findings in PsA, but in OA they appear frequently. A site for bone spurs that’s difficult to differentiate is the vertebral column — pinpointing which type of arthritis is responsible can be tricky. In this type of case, clinical aspects, blood tests, and imaging can help a doctor establish the diagnosis.

One joint symptom that is not shared with both conditions is unusual sounds, like crunching or grinding, that people with OA may experience. Referred to as crepitus, noisy joints do not occur with PsA.

3. Unlike Osteoarthritis, Psoriatic Arthritis Has Non-Joint Symptoms

Because PsA is a systemic disease, it can cause a slew of symptoms not seen in people with OA. PsA may also cause:

• Fatigue
• Psoriatic changes to the nails, such as pitting, or holes, and separation from the nail bed and of the skin
• Dactylitis (swelling in fingers and toes)
• Uveitis (inflammation of the eyes)
• Enthesitis (inflammation of entheses a structure connecting tendons and ligaments to bones)
• Inflammatory bowel disease (which can frequently be associated)

4. The Causes of Each Condition Are Distinct

PsA and OA differ distinctly in what causes them.

What Causes Osteoarthritis?

Aging and wear and tear on the joints lead to OA. Layers of protection inside the joints break down, causing bones to rub against one another. This friction causes pain and can change the shape of the joint over time. People who overuse a specific joint or set of joints for their work or in sports are more likely to end up with OA and develop it earlier. Injury to a joint may also eventually cause OA.

The exact mechanism of how the joint breaks down is unknown. More research is needed to understand exactly how, why, and when this happens, as well as why it occurs in some people but not others.

What Causes Psoriatic Arthritis?

The cause of PsA is not well understood. However, rheumatologists and researchers believe that a combination of biological (genetic) and environmental risk factors can trigger the onset of PsA.

5. They Are Diagnosed in Different Ways

Beyond closely assessing pain and swelling patterns, there are a few ways that a doctor or rheumatology expert can differentiate between PsA and OA.

Imaging Tests for Psoriatic Arthritis and Osteoarthritis

Imaging tests, such as X-rays, ultrasound, and MRI, can help with diagnosing both PsA and OA and determining how far the disease has advanced.

X-rays are the first line of diagnosis for both conditions. More sensitive technologies, like MRI, cost more and are therefore used as second-line diagnostic tools.

Ultrasound imagery can be useful in recognizing specific inflammatory patterns that occur in PsA. These may be ordered if other test results are inconclusive.

Blood Tests for Psoriatic Arthritis

Blood tests can help identify inflammatory markers, such as erythrocyte sedimentation rate and C reactive protein that have high serum levels when PsA is active. PsA does not have specific autoimmune markers, whereas rheumatoid arthritis, for example, has rheumatoid factor and cyclic citrullinated peptide antibodies.

Checking for signs of inflammation in your blood can help your doctor figure out why your joints hurt or eliminate other possible health issues that present similarly. Osteoarthritis doesn’t show signs in blood tests. Also, if your doctor sees no signs of inflammation in areas you’re experiencing pain, they may determine you have OA.

Joint Fluid Analysis

Looking at the fluid in the joints can help confirm a diagnosis of PsA. Your rheumatologist will remove a bit of the affected joint’s fluid, which will be analyzed for clues to the cause of your joint pain.

6. Disease-Modifying Drugs Are an Option for Treating Psoriatic Arthritis

Disease-modifying antirheumatic drugs (DMARDs) have been proven in clinical studies to stop or slow disease progression in people with inflammatory arthritis. Methotrexate (sold as Otrexup, Rasuvo, and Trexall) is one of the most commonly prescribed medications in this category. Biologic DMARDs, such as etanercept (Enbrel), infliximab (Remicade), and adalimumab (Humira), are approved by the U.S. Food and Drug Administration (FDA) for PsA. Some of these drugs may be taken along with methotrexate.

Biologic DMARDs may be given for severe cases of PsA or when other drugs haven’t worked. Similarly, immunomodulators like abatacept (Orencia) and tofacitinib (Xeljanz), which target specific immune responses that cause joint inflammation, can be effective for PsA.

These drugs aren’t helping in treating OA, because the joint changes in OA are caused by mechanical triggers (physical stressors), not inflammation. Treatment of OA is mainly based on eliminating or avoiding the trigger, as well as using over-the-counter anti-inflammatories — or in more severe cases, short-term use of corticosteroids and physical and occupational therapy.

2 Similarities Between Psoriatic Arthritis and Osteoarthritis

There’s some overlap in the symptoms and treatments used for PsA and OA.

1. They Both Cause Joint Symptoms

Most people who develop PsA experience the skin symptoms first, although some individuals with PsA never have psoriasis symptoms. In the United States, about 30 percent of people with psoriasis also have PsA.

The severity of a person’s psoriasis symptoms is not linked to the severity of their PsA symptoms. Some people may have severe skin lesions but mild PsA symptoms, and others may have mild lesions but severe joint pain.

Both people with PsA and those with OA will likely experience joint pain. However, differences in the pain can help differentiate between the two conditions.

2. Many Treatments Overlap

The treatment of psoriatic arthritis and osteoarthritis often overlaps, including many anti-inflammatory drugs and physical therapy.

Nonsteroidal Anti-Inflammatory Drugs

Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen, can help manage mild to moderate symptoms of both PsA and OA. These drugs help reduce pain, inflammation, and swelling.

Corticosteroid Injections

Corticosteroids injected into the affected joint can provide quick relief for PsA and OA symptoms. However, because of the side effects associated with steroid injections and other steroid use (oral steroids, in particular), these medications are not a good long-term option for treating joint pain.

Physical and Occupational Therapy

People diagnosed with PsA and OA often benefit from both occupational and physical therapy. Physical therapists can help develop exercise plans that won’t make your arthritis symptoms feel worse. Certain exercises may also help boost flexibility and ease stiffness and joint pain.

Occupational therapists can help you make lifestyle changes so you can go through your daily activities without further damaging joints or experiencing pain.

Is It Possible To Have Both Psoriatic Arthritis and Osteoarthritis?

You can have psoriatic arthritis and osteoarthritis together and in the same joints. One MyPsoriasisTeam member said they experience both conditions at once, along with fibromyalgia (a chronic condition that causes bodywide pain, fatigue, and other symptoms).

If you think you are living with PsA, OA, or both, it’s important to see a health care provider soon. They can help you through the diagnostic process and then work with you to find a treatment plan that will be effective and work for your body.

Find Your Team

MyPsoriasisTeam is the social network for people with psoriasis and psoriatic arthritis and their loved ones. On MyPsoriasisTeam, more than 125,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis and psoriatic arthritis.

Do you live with PsA and wonder if you have OA, too? Maybe you have been diagnosed with both conditions, and you’re learning how to live with them. Share your thoughts or questions in the comments below or by posting on your Activities page.