Psoriatic arthritis (PsA) is an autoimmune condition that affects some people with psoriasis. Osteoarthritis (OA) is a degenerative condition that involves cartilage at the end of bones wearing away.

“Arthritis” describes more than 100 health conditions that cause joint pain or damage. OA is the most common type, affecting more than 32.5 million adults in the United States.

PsA and OA can cause some of the same symptoms. Below, we explore what these two types of arthritis have in common, as well as their key differences.

Below, learn what a person with PsA or OA may experience.

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PsA symptoms

People with PsA may have:

Symptoms of PsA typically affect the following parts of the body:

  • ankles
  • fingers
  • knees
  • lower back
  • toes

Below is a 3D model of PsA. It is fully interactive, and people can explore it with their trackpad or touchscreen.

OA symptoms

Symptoms of OA vary and depend on the part of the body affected. A person with OA generally has:

  • painful and stiff joints, especially after resting or overexertion
  • a clicking or crunching sound or feeling when the joints bend
  • noticeable bony lumps, called bone spurs, near the affected joints
  • changes in the shape of the joints

OA can develop in any joint, but it often occurs in the:

  • hands
  • hips
  • knees
  • lower back
  • neck
  • feet

The following factors can help a person differentiate between PsA and OA:

Skin symptoms

PsA is associated with psoriasis, a skin condition that causes itchy, scaly rashes. Patches of skin may also thicken and change color, becoming silvery-white in some cases. These skin changes can help doctors confirm a PsA diagnosis.

Nail changes

Psoriasis and PsA can cause the nails to become pitted or lift from their nail beds. Roughly 50% of people with PsA have discolored, pitted, or thickened nails. Nail changes are not associated with OA.

Flares

PsA symptoms typically flare up and ease off, though they gradually worsen.

OA symptoms can flare up, but they are more likely to be consistent as the wearing away of cartilage changes the shapes of the affected joints.

OA flares — times when symptoms are worse than usual — tend to follow periods of increased stress or exertion. For example, if a person stands for long periods, and this is atypical for them, the added weight on the knee joint may trigger OA symptoms.

Swollen fingers and toes

PsA is an inflammatory condition that causes swelling of the fingers and toes, which may come to resemble sausages.

Inflammation is not typically a significant symptom of OA, although it may occur around the affected joints. In this case, the inflammation usually affects a single finger or toe during a flare.

Joint deformity

OA is associated with:

  • the degeneration of cartilage at the end of bones
  • the development of bone spurs, lumps of bone, around the affected joints
  • inflammatory nodules in the small joints of the hands

Bone spurs can cause the joints to take on an atypical shape. Due to a lack of cartilage, the affected joints also tend to click or crack. As the cartilage wears away, the exposure of small nerve fibers in the joint can lead to pain during movement or when putting weight on the joint.

Eye symptoms

People with PsA may have inflamed, irritated eyes. The condition can also cause changes in vision and pain in the eye area. Eye inflammation is not a symptom of OA.

Very different factors cause these two forms of arthritis.

PsA causes

PsA is an inflammatory autoimmune condition. Inflammation and the resulting symptoms stem from overactivity of the immune system, but scientists are still unsure about why or how this develops.

Genetic and environmental factors also seem to play a role, as do the microbiota — or microorganism communities — of the skin and gastrointestinal tract.

PsA occurs in people with the skin condition psoriasis. Around 30% of people with psoriasis develop PsA, usually 8–10 years after their skin symptoms appear. However, about 10–15% of people with PsA may experience the symptoms in their joints before their skin symptoms develop.

OA causes

OA results from the gradual breakdown of cartilage at the end of bones. Cartilage is a flexible, slippery tissue that cushions and protects bones, allowing them to move without friction.

If the cartilage completely wears away, the friction of bone rubbing against bone results in pain, stiffness, and a reduced range of motion. It also causes irreversible damage to joints and bones.

OA can develop when a person uses a joint repeatedly, for example, at work or during a sport. OA may also result from obesity, which can put additional strain on joints.

Additionally, genetic factors may play a role. A person may have a higher risk of developing OA if a close family member has the condition.

There is an increasing amount of evidence that inflammation may also contribute to OA.

Below, we explore what can increase the chances of developing these two forms of arthritis.

PsA risk factors

Factors that increase the likelihood of developing PsA include:

  • Age: PsA tends to occur in people aged 30–50 years, though it can develop at any age.
  • Genes: About 40% of people who develop PsA have a family member with either PsA or psoriasis.
  • Health status: Sometimes, an infection can trigger an immune response that leads to PsA.

OA risk factors

Factors that increase the likelihood of developing OA include:

  • Age: Older adults are more likely to have OA.
  • Genes: If a family member has OA, a person has a higher risk of developing it.
  • Sex: Females, especially those over 50 years old, are more prone to OA.
  • Weight: Obesity places added strain on the joints, and this can contribute to OA. Body fat can also produce proteins that cause inflammation in joints.
  • Joint damage: A history of injury or repetitive movements, for example, while playing sports, can increase the risk of OA.

There is currently no cure for PsA or OA, but various treatments can relieve the symptoms and help prevent further damage.

PsA treatments

Ways of managing this type of arthritis include:

Medications

The first-line treatment for most people with a new diagnosis of PsA is biologic therapy. These drugs target a specific part of the immune system to treat the underlying cause of PsA. However, not everyone can use these medications because of the risk of adverse effects.

Alternatives include oral small-molecule drugs and disease-modifying antirheumatic drugs. These systemic treatments work throughout the body to reduce inflammation or suppress the immune system.

Treatments for symptoms include:

Surgery

A surgeon may replace a severely damaged joint with a prosthetic one made of plastic and metal.

Home care strategies

The following steps may help:

  • engaging in regular exercise to build up muscle and encourage joint flexibility
  • managing body weight, if necessary, to reduce stress on the joints
  • choosing foods that may help prevent inflammation, such as fresh fruits and vegetables
  • getting enough sleep to counteract the fatigue that medications and chronic illness can cause
  • seeking emotional support, if necessary
  • quitting smoking, if necessary, and avoiding secondhand smoke, as smoking can reduce the response to treatment and increase the risk of other health conditions

OA treatments

Ways of managing this type of arthritis include:

Medication

Some drugs that can relieve pain due to OA include:

  • acetaminophen (Tylenol)
  • NSAIDs, in tablet or topical forms
  • corticosteroid injections, which a person can have three or four times a year

Therapies

A doctor may recommend physical therapy and occupational therapy for someone with OA.

A physical therapist can develop a program that aims to reduce pain, strengthen the muscles, and increase the range of motion. An occupational therapist can teach people to reduce pressure on their joints while doing everyday tasks.

Surgery

Surgery may not be suitable for everyone. It involves replacing a severely damaged joint with a prosthetic one.

Home care strategies

Some steps to take include:

  • doing regular exercise to strengthen the muscles around the joint
  • maintaining a moderate body weight to reduce stress on the joint
  • applying hot and cold compresses to reduce pain
  • supporting weak joints with braces, shoe inserts, and taping techniques
  • using equipment such as canes, walkers, and grabbing devices
  • receiving emotional support, if necessary

Below are answers to some questions people often ask about PsA and OA.

Is PsA a risk factor for OA?

A person with PsA can also develop OA, but they do not have a higher risk than anyone else.

Which joints does PsA mostly affect?

PsA can affect any joint. It commonly affects the small joints in the hands and feet, but it can also affect the knees, ankles, elbows, wrists, neck, and sacroiliac joints, where the spine meets the pelvis. A hallmark sign of PsA is inflammation in the distal interphalangeal (DIP) joints. The DIP joints are those closest to the tips of the fingers, toes, and thumbs.

What conditions can people confuse PsA with?

Other types of inflammatory arthritis that can resemble PsA include rheumatoid arthritis, reactive arthritis, and ankylosing spondylitis. Doctors do not consider OA an inflammatory arthritis. However, it can also cause joint pain.

Some 68% of people who develop PsA have a history of psoriasis. Hallmark symptoms of PsA include sausage-like swelling in the fingers and toes and inflammation in the joints closest to the fingertips.

Psoriatic arthritis and osteoarthritis are types of arthritis. Both cause joint pain, and a person can manage this symptom and others with medications, home care strategies, and, if necessary, surgery. There is currently no cure for either condition.

A doctor can offer advice to anyone experiencing persistently painful, swollen, or stiff joints and provide treatment, if necessary. Receiving treatment can ease the symptoms and help keep them from worsening.