Rheumatoid arthritis and osteoarthritis both cause joint pain and stiffness. They are both forms of arthritis but have different causes and treatments.

There are more than 100 types of arthritis and related diseases. Two of the most common types are rheumatoid arthritis (RA) and osteoarthritis (OA).

OA is more common than RA. Both involve inflammation in the joints, but RA causes much more inflammation. Until recently, experts believed that inflammation was not a feature of OA, and researchers are still investigating the role that it plays in the illness — whether it is a cause or a result of the condition.

OA and RA share some symptoms, but RA can affect multiple joints, and it tends to develop symmetrically, on both sides of the body. OA usually affects a few joints, and it typically only develops on one side.

Also, RA involves systemic inflammation and can cause a fever and other flu-like symptoms. The symptoms of OA tend to be limited to the affected joint or joints.

Below, we explore the similarities and differences between RA and OA in more detail, looking at their symptoms, causes, and treatments.

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Joints contain protective tissues that prevent the bones from scraping against one another. For example, cartilage sits over the bones to facilitate smooth movement in the joint.

Arthritis damages this protective tissue. But in RA and OA, the causes of joint damage are different.

RA is an autoimmune disease. It occurs when a person’s immune system mistakenly attacks healthy tissues in the joints. In the process, it releases enzymes that destroy the linings of the joints, leading to pain, swelling, and stiffness. Other symptoms can also develop throughout the body.

OA involves the protective cartilage gradually wearing down, causing the bones to rub together. This wear and tear can result from repetitive movements, such as in sports, that place pressure on the joints. Bony growths called bone spurs develop on the joints, which become stiff, painful, and harder to move.

The risks of developing OA and RA increase with age, although either condition can occur at any age.

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RA and OA can cause some of the same symptoms, including:

  • joint pain
  • stiffness in joints
  • swelling, which is more severe in RA
  • restricted mobility in affected joints

Symptoms of both conditions tend to be worse in the morning. Both can cause stiffness in the morning or after resting, too. However, in a person with OA, the stiffness usually improves within 30 minutes. In someone with RA, it usually lasts longer.

RA symptoms may develop and worsen quickly, sometimes within a few weeks. OA symptoms arise more slowly, as the protective tissues in the joints gradually wear down. However, certain activities can cause a sudden worsening of OA symptoms. For example, going for a hike may cause sudden, severe swelling in the knee.

Both conditions can affect many different joints in the body. OA is most likely to develop in the knees and the small finger and thumb joints. RA often develops in the hands, fingers, elbows, knees, feet, and hips, and it usually occurs in the same joints on both sides of the body. OA, meanwhile, often only develops on one side.

Overall, OA is localized — it only affects the joint and its surrounding tissues. People with the condition may develop bone spurs or other bone abnormalities, however. For example, OA in the hands often causes small lumps to develop around the ends of the finger joints.

RA commonly affects multiple joints, causing tenderness, swelling, and stiffness. Also, nodules can develop around the affected joints. RA is systemic, rather than localized, so it can also cause:

  • fatigue
  • a fever
  • weight loss
  • inflammation beyond the joints, such as in the eyes and lungs

A doctor who suspects that a person has RA or OA performs a physical examination, takes a medical history, and does various diagnostic tests.

Diagnosing these conditions can be challenging because the symptoms often overlap, particularly in the early stages.

Blood tests for RA can help confirm or rule out the diagnosis. These tests look for different biomarkers in the blood, such as cyclic citrullinated peptide antibody and rheumatoid factor. A doctor may also check levels of the C-reactive protein antibody, a marker that indicates inflammation.

In addition, a doctor may order X-rays, MRI scans, ultrasound scans, or a combination to determine the extent and location of damage from RA or OA.

RA and OA are chronic conditions, which means that they do not go away. There is currently no cure, but treatments can help a person manage their symptoms, improve their quality of life, and slow the progression of the condition.

Treatment may involve using medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation. This can help alleviate pain and stiffness and improve the range of motion.

Doctors may also recommend steroid-based medications to reduce inflammation. For example, they may inject steroids directly into the affected joints when it is important to reduce inflammation immediately.

To treat RA, the American College of Rheumatology recommends using disease-modifying antirheumatic drugs (DMARDs), often alongside NSAIDs or steroids and biologic medications. DMARDs aim to suppress the immune system and reduce its damage to tissues in the joints.

The treatment plans for RA and OA also often involve physical therapy. This helps improve mobility and keep the joints flexible.

Having a healthy diet and sticking to an appropriate exercise plan can also help. Maintaining a healthy weight can help prevent excess pressure on the joints. Quitting smoking and avoiding secondhand smoke are also a good idea, particularly for people with RA.

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RA and OA are chronic conditions that cause pain and stiffness in the joints. Both can worsen over time without appropriate treatment. The effects of OA and RA on a person’s daily life can range from mild to severe.

The two conditions can cause similar symptoms, but they have different causes and treatments. OA usually affects fewer joints, and its symptoms are generally limited to the joints. The progression of RA is more difficult to predict, and it can cause more widespread symptoms.

The outlook for people with RA has greatly improved due to advances in research and therapies. Doctors can usually prevent or slow the progression of the disease with effective treatment.