Osteoarthritis vs. Rheumatoid Arthritis: Key Differences

Osteoarthritis (OA) is the most common type of arthritis, with an OA diagnosis believed to affect more than 32 million people in the United States. Rheumatoid arthritis (RA), a more rare but disabling type of arthritis, affects an estimated 1.5 million people in the U.S.

While they both fall under the "arthritis" umbrella and share certain similarities, these diseases have significant differences. Osteoarthritis is caused by the breakdown of cartilage that cushions your joints. Rheumatoid arthritis is an autoimmune disease in which your immune system attacks your body's own tissues in the joints.

This article discusses the differences between OA and RA, their respective causes, and how they are diagnosed and treated by healthcare providers. It also identifies risk factors for arthritis.

OA and RA: Key Comparisons

Osteoarthritis is a degenerative joint disease. It's often called wear-and-tear arthritis and is caused by cartilage loss. Cartilage is the cushioning that sits between the bones that form your joints. When it wears away or deteriorates, it causes your bones to rub together, which is extremely painful.

Osteoarthritis typically begins in a single joint and is more common after age 65.

The less-common rheumatoid arthritis is a chronic, inflammatory, autoimmune disease that primarily targets the lining of the joint (synovium), but it can also affect the organs throughout your body. Multiple joints are usually involved as well.

RA disease onset is most common in people between 30 and 60. Assigned females are two to three times more likely than males to have the disease, and assigned males tend to get it later in life.

Symptoms of OA and RA

OA and RA have some symptoms in common. However, each condition also has several symptoms that are different from the other.

Common symptoms of osteoarthritis include:

• Pain in the affected joint after repetitive use or activity
• Morning stiffness that lasts a half hour or less
• Joint pain that is often worse later in the day
• Swelling and stiffening of the affected joint after prolonged inactivity
• Bone spurs, bony enlargements (Heberden's nodes and Bouchard's nodes in the hands), and limited range of motion

Rheumatoid arthritis symptoms include:

• Joint pain
• Joint swelling or effusion
• Joint stiffness
• Redness and/or warmth near the joint
• Restricted range of motion
• Morning stiffness lasting more than an hour
• Involvement of the small joints of the hands and feet
• Extreme fatigue
• Rheumatoid nodules
• Symmetrical joint involvement (e.g., both knees, not just one)
• Lung, kidney, or cardiac involvement

Osteoarthritis pain tends to start slowly with joint pain and gradually increase in symptoms through the months and years. RA may start with symptoms like fatigue, fever, and weakness. The joint pain may get worse over a few weeks or months.

Some symptoms of RA and OA are similar but present differently. For example, both conditions include morning stiffness. However, with OA, it tends to last for a shorter time than RA.

Joints Affected With OA

Since OA is more likely to arise with age and develop over time, it tends to affect joints like knees and hips that have seen a lifetime of use. It also may affect joints that have been injured, or subject to repetitive motion and overuse, like hands and wrists.

Keep in mind that because OA is a degenerative disorder, it also can affect other joints. Pain in your back, for example, may be due to OA affecting the joints in your spine.

Joints Affected With RA

You may first notice rheumatoid arthritis in the knee, where symptoms are common, but RA can affect multiple joints throughout the body. A 2022 study of 1,458 people with an RA diagnosis (two-thirds of them women) found the symptoms often affected the wrist and ankle as the disease progressed, while also affecting hips and elbows.

Risk Factors

There are some similarities among risk factors for OA and RA. For example, genetics can play a role in RA. Genetics also can contribute to the risk of developing OA. In both types of arthritis, though, a family history of diagnosis does not necessarily mean you'll eventually have either type.

Additional risk factors for RA also can include:

• Lifestyle factors including diet, weight, and smoking. Smoking for 20 years can make it twice as likely that someone will develop RA.
• Environmental exposures, including toxins, illness, and infection
• Sex and gender, with RA three times more likely to affect people assigned female at birth

Additional risk factors for OA include:

• Age, with cumulative wear and tear on joints
• A history of injury or overuse with affected joints
• Sex and gender (more likely in assigned females)
• Obesity and extra weight
• Race (some Asian groups have lower rates)

Certain jobs that lead to joint strain or repetitive motion injury also can contribute to developing OA, as can an underlying illness like diabetes.

Causes

OA and RA have different causes, although the theories behind both are still under scientific investigation.

Osteoarthritis Causes

OA was long thought to solely be caused by normal wear-and-tear or the effects of aging. However, experts now know that other factors can contribute to your risk of developing OA, including:

• Joint injury
• Repetitive joint use or stress
• Being overweight
• A family history of osteoarthritis

In addition, it's been discovered that the water content of cartilage initially increases with osteoarthritis while the protein composition of cartilage steadily degenerates. This is believed to be due to an imbalance in your body's ability to repair cartilage as it deteriorates. Thus far, the cause of this imbalance is unknown.

Rheumatoid Arthritis Causes

The cause of RA is less understood. Researchers have worked for years to find the cause of the abnormal autoimmune response associated with the disease but have yet to find a single clear cause. Common theories point to a genetic predisposition combined with other possible triggers, such as smoking or obesity.

Diagnosis

If you're experiencing any arthritis symptoms, make an appointment with your healthcare provider. They can help you determine whether they're signs of osteoarthritis or rheumatoid arthritis.

The diagnostic processes for OA and RA have a fair amount of overlap. Test results, a physical examination, and your medical history are all taken together to determine a diagnosis.

• X-rays of affected joints can show joint damage associated with both osteoarthritis and rheumatoid arthritis.
• Arthrocentesis, which involves removal and analysis of joint fluid, can evaluate for either condition, with the results differentiating which type of arthritis you have.
• Blood tests cannot definitively diagnose osteoarthritis, but they may be used to rule out other conditions, including rheumatoid arthritis.

Laboratory tests that are commonly ordered to help diagnose (or rule out) rheumatoid arthritis, as well as other inflammatory or autoimmune diseases, include:

• Rheumatoid factor (RF)
• Erythrocyte sedimentation rate (ESR or sed rate)
• C-reactive protein (CRP)
• Anti-CCP test
• Antinuclear antibody (ANA)

A proper diagnosis is essential to finding the right treatments.

Treatments

OA and RA are treated very differently.

OA Treatment Options

Treatment options for osteoarthritis focus on pain relief and restoring function to the affected joint. Common medications for reducing pain and inflammation include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Analgesics (painkillers)

Other treatment options are:

• Physical therapy to strengthen and stabilize the joint
• Support/bracing
• Heat
• Rest
• Alternative treatments such as massage therapy and acupuncture

RA Treatment Options

The primary treatment for rheumatoid arthritis is medication to reduce immune system activity and inflammation. Five categories of drugs commonly used to treat rheumatoid arthritis are:

• Disease-modifying anti-rheumatic drugs (DMARDs), such as methotrexate
• Biologics, such as Enbrel (etanercept), Remicade (infliximab), Humira (adalimumab), Rituxan (rituximab), Orencia (abatacept), toclizumab, and JAK inhibitors
• Corticosteroids, such as prednisone and hydrocortisone
• NSAIDs, such as Celebrex (celecoxib) and naproxen
• Analgesics (painkillers)

For both conditions, steroid injections may help with inflammation and pain in your joints.

Managing weight may also help with reducing strain on your joints in both RA and OA. Staying at a healthy weight can also help reduce inflammation in autoimmune diseases such as RA.

For serious cases of either condition, the last-resort treatment option is surgery. This includes arthroscopy, arthrodesis (fusion), and arthroplasty (joint replacement).

Summary

OA and RA may have similar symptoms, but they are two very different conditions. Osteoarthritis is caused by the wearing down of cartilage in the joints. Rheumatoid arthritis is an autoimmune disease where the immune system attacks tissues in the joints.

Symptoms can be similar, but there are differences between RA and OA. While OA tends to start with joint pain, RA may start with other symptoms like fatigue and fever. It is also possible to have both OA and RA, which requires treating both at the same time.

Treatment for OA tends to focus on pain relief. Treatment for RA includes several different medications to treat this autoimmune disease. Talk to your healthcare provider about your symptoms to get an accurate diagnosis and learn about your treatment options.