How Rheumatoid Arthritis and Osteoarthritis Differ

Arthritis is a general term that covers more than 100 diseases and related conditions.¹ Inflammation and joint stiffness are at the heart of all forms of arthritis. Arthritic pain may be constant or may come and go. It may occur when at rest or while moving. Pain may affect only 1 joint or show up in different parts of the body. The skin over the affected joint may become red and swollen, and feel warm to the touch.

According to the Arthritis Foundation, rheumatoid arthritis (RA) and osteoarthritis (OA) are the most common types of arthritis, affecting 1.5 million and 27 million Americans, respectively.^2,3 These conditions damage joints and affect their function, and although they have some similarities, they are very different diseases, particularly in terms of their causes and their management and treatment.

Table 1: Risk Factors for Osteoarthritis

Excess weight

Age

Previous joint injury

Joints that are not properly formed

Family history

Stress on the joints from certain jobs or sports

Causes

OA is caused by aging and regular wear and tear (Online Table 1). In OA, the cushioning cartilage that covers bone joints gradually wears away, which allows bone to rub against bone, leading to swollen joints and painful movement. OA is sometimes called degenerative joint disease or degenerative arthritis. RA occurs when your immune system, which normally defends the body from invading organisms, mistakenly attacks the lining of your joints, causing pain, swelling, warmth, redness, stiffness, and loss of function in the joints, all of which can eventually result in joint deformity (Online Table 2).

Table 2: Risk Factors for Rheumatoid Arthritis

Sex: women are 2 to 3 times more likely than men to develop RA

Age: RA most commonly begins between 40 and 60 years of age

Family history: if a family member has RA, you may have an increased risk

^{RA = rheumatoid arthritis.}

Symptoms

Although both RA and OA can affect the small joints of the hand, there are differences. RA develops relatively quickly over a period of weeks to months and tends to affect the middle joints of the fingers and the knuckle joints (Online Table 3). RA can sometimes affect other organs of the body, such as the skin, eyes, lungs, and blood vessels.

Table 3: Signs and Symptoms of Rheumatoid Arthritis

Tender, warm, swollen joints

Morning stiffness that may last for hours

Firm bumps of tissue under the skin on your arms (rheumatoid nodules)

Fatigue, fever, and weight loss

OA starts slowly, commonly affecting the joints near the ends of the fingers and at the base of the thumb (Online Table 4), and can occur in any joint, but usually affects the hands, knees, hips, or spine. In RA, the same joints are usually affected on both sides of the body. This symmetry does not typically occur in OA, so it is common for only 1 hand or knee to be painful.

Table 4: Signs and Symptoms of Osteoarthritis

Pain

Tenderness

Stiffness

Loss of flexibility

Grating sensation in joints

Bone spurs around affected joint

Joints damaged by OA may be stiff in the morning, but they usually feel better within an hour. Joints affected by RA, however, often hurt for more than an hour after getting out of bed.

Diagnosis

No single test can diagnose OA. Your health care provider (HCP) may use your medical history, a physical exam, imaging tests, and other blood or laboratory tests to rule out other conditions that might be causing symptoms. Your HCP also may order a test in which fluid is drawn from the joint to rule out infection or gout.

RA can be difficult to diagnose in its early stages because the early signs and symptoms mimic those of many other diseases, including other types of arthritis. As with OA, there is no single blood test or physical finding to confirm an RA diagnosis. An HCP will conduct a physical exam and obtain a personal and family medical history. During the exam, your HCP will check your joints for swelling, redness, and warmth, and your reflexes and muscle strength.

Blood tests can measure inflammation levels and look for biomarkers, such as antibodies (blood proteins) linked with RA. Individuals with RA tend to have an elevated erythrocyte sedimentation rate (ESR, or sed rate) and/ or a high C-reactive protein (CRP) level. Both of these markers indicate the presence of an inflammatory process in the body.

An x-ray, ultrasound, or magnetic resonance imaging scan may be necessary to look for joint damage, such as erosion, which is a loss of bone within the joint and narrowing of joint space. Your HCP may also recommend imaging tests to help track the progression of RA in your joints over time.

Medications Used to Treat OA

Acetaminophen (eg, Tylenol) can relieve pain, but does not reduce inflammation. It is effective for individuals with OA who have mild to moderate pain. Do not take more than the recommended dosage.

Nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce inflammation and relieve pain associated with OA. OTC NSAIDs include ibuprofen (Advil, Motrin IB, others) and naproxen (Aleve, others). Topical NSAIDS have fewer adverse effects and may relieve pain just as well.

Prescription NSAIDS include celecoxib (Celebrex), meloxicam (Mobic), indomethacin (Indocin, Tivorbex), and diclofenac (eg, Voltaren, Cataflam, Pennsaid).

Corticosteroids reduce inflammation associated with OA, but should not be taken for a long time.

Medications Used to Treat RA

NSAIDs can relieve pain and reduce inflammation. OTC NSAIDs include ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve). Stronger NSAIDs are available by prescription.

Corticosteroid medications, such as prednisone, reduce inflammation and pain, and slow joint damage. Steroids are usually used for only a short time.

Disease-modifying antirheumatic drugs (DMARDs) can slow the progression of RA and save the joints and other tissues from permanent damage. Common DMARDs include methotrexate (Trexall), leflunomide (Arava), hydroxychloroquine (Plaquenil), and sulfasalazine (Azulfidine).

Biologic agents, also known as biologic response modifiers, is a newer class of DMARDs that includes abatacept (Orencia), adalimumab (Humira), anakinra (Kineret), certolizumab (Cimzia), etanercept (Enbrel), golimumab (Simponi), infliximab (Remicade), rituximab (Rituxan), and tocilizumab (Actemra). Tofacitinib (Xeljanz), a new synthetic DMARD, is also available in the United States. Biologic agents can target parts of the immune system that trigger inflammation that causes joint and tissue damage.

Treatment plans for OA and RA involve combinations of exercise, weight control, rest, joint care, nondrug pain relief techniques to control pain, complementary and alternative therapies, and surgery. Symptoms may gradually worsen over time, but staying active and maintaining a healthy weight can improve symptoms. Medications and other treatments can slow the progression of OA and RA. Having a network of friends, family members, and coworkers can provide emotional support and can help you cope with changes and pain due to OA or RA, as well.

Resources

• Arthritis in general. Centers for Disease Control and Prevention website. cdc.gov/arthritis/basics/general.htm.
• Comparing rheumatoid arthritis and osteoarthritis: topic overview. WebMD website. webmd.com/rheumatoid-arthritis/tc/comparing-rheumatoid-arthritis-and-osteoarthritis-topic-overview.
• What is osteoarthritis? National Institute of Arthritis and Musculoskeletal and Skin Diseases website. niams.nih.gov/health_info/Osteoarthritis/osteoarthritis_ff.asp#a.
• The difference between rheumatoid arthritis and osteoarthritis. Mayo Clinic website. mayoclinic.org/diseases-conditions/rheumatoid-arthritis/in-depth/differencebetween-rheumatoid-arthritis-and-osteoarthritis/art-20091920.
• Rheumatoid arthritis risk factors. Mayo Clinic website. mayoclinic.org/diseasesconditions/rheumatoid-arthritis/basics/risk-factors/con-20014868.

Beth is a clinical pharmacist and medical editor residing in northern California.

References

• What is arthritis? Arthritis Foundation website. arthritis.org/about-arthritis/understanding-arthritis/what-is-arthritis.php. Accessed January 14, 2016.
• What is osteoarthritis? Arthritis Foundation website. arthritis.org/about-arthritis/types/osteoarthritis/what-is-osteoarthritis.php. Accessed January 14, 2016.
• What is rheumatoid arthritis? Arthritis Foundation website. arthritis.org/about-arthritis/types/rheumatoid-arthritis/what-is-rheumatoid-arthritis.php. Accessed January 14, 2016.