What is rheumatoid arthritis?

Rheumatoid arthritis¹ is a chronic inflammatory autoimmune disease. In people with this condition (as with other immune disorders), the immune system mistakenly attacks healthy parts of the body, causing inflammation.

In the case of rheumatoid arthritis, the immune system mainly targets the cells in the lining of the body’s joints (most commonly, those in the knees, wrists, and hands). This causes the joints to become painful, swollen, and stiff.

The inflammation caused by rheumatoid arthritis can damage other tissues in the joints, potentially becoming so severe as to cause bone erosion. In some cases, this damage can be reversed or mitigated. When damage has progressed, however, it can result in a number of problems, including chronic pain, misshapen joints (deformities), and a lack of balance.

Rheumatoid arthritis differs from “regular” arthritis (osteoarthritis, the most common form of the disease) in its causes and effects. Osteoarthritis is caused by wear and tear on the joint and involves the degeneration of bone cartilage (a connective tissue that cushions and protects the bones in a joint). Rheumatoid arthritis, on the other hand, is caused by immune dysfunction and targets the lining of the joints (called the synovial membrane).

While the most common symptoms of rheumatoid arthritis occur in the joints, the condition can also cause inflammation and damage in other bodily systems and organs, including the eyes, heart, lungs, skin, and blood vessels.

How common is rheumatoid arthritis?

Rheumatoid arthritis affects at least 1.3 million² Americans, making it the most common form of autoimmune arthritis. Approximately 75% of those diagnosed with rheumatoid arthritis are women, and between 1–3% of women will develop the disease at some point in their lives.

People can be diagnosed with rheumatoid arthritis at any age. However, the most common window for being diagnosed with the condition is between the ages of 30 and 50. Regardless of age, anyone experiencing the symptoms of arthritis should see their healthcare provider, as early detection and treatment can be key to slowing the progression of the disease.

Osteoarthritis vs. rheumatoid arthritis

There are several key differences³ between osteoarthritis (or “regular”) arthritis and rheumatoid arthritis, the most notable being their causes.

Osteoarthritis is caused by wear on the joints, caused either by normal degradation over time or as the result of an injury. Rheumatoid arthritis, however, occurs when a person’s immune system attacks their own cells, causing inflammation and joint damage.

Other major differences between the two conditions include:

• Age of onset: Rheumatoid arthritis can begin at any time during one’s life, while osteoarthritis usually begins later in life after the joints have had time to sustain damage.
• Signs and symptoms: Joints affected by rheumatoid arthritis are usually stiff, painful, and swollen. In osteoarthritis, however, the joints ache and may be tender to the touch but generally don’t become swollen.

Both types of arthritis also cause stiffness in the joints in the morning. However, in rheumatoid arthritis, this stiffness usually lasts longer than an hour, while in osteoarthritis, it usually improves in less than an hour.

Rheumatoid arthritis may cause extreme fatigue. People with the condition may feel like they are ill most of the time. Conversely, those with osteoarthritis generally don’t experience any arthritis-related symptoms that go beyond joint problems.

• Rate of onset and progression: Rheumatoid arthritis often comes on quickly over a period of months or weeks. Osteoarthritis, on the other hand, generally develops over the course of a few years. Additionally, because osteoarthritis is a progressive disease, its symptoms gradually worsen over the course of one’s life.
• Areas of the body affected: Rheumatoid arthritis can affect both small and large joints, and usually does so on both sides of the body at once (e.g., both hands, both knees). Osteoarthritis often starts in one joint that has sustained sufficient damage and only affects other joints as they, too, undergo enough damage to cause pain.

Rheumatoid arthritis causes

Rheumatoid arthritis occurs⁴ when the body’s immune system attacks its own healthy tissue—specifically, the synovium. The synovium is the membrane lining that surrounds all joints in the human body.

This attack causes significant inflammation in the synovium. Over time, chronic inflammation causes the synovium to become thicker. This thickening can eventually displace and destroy both cartilage and bone in a joint.

When the synovium thickens and the cartilage and bone are damaged, the ligaments and tendons that compress the joint and help it move properly start to stretch. Over time, the joint can lose both its shape and its alignment.

There is likely a genetic component to rheumatoid arthritis, though genes alone do not seem to cause the condition. It is thought that certain environmental factors, combined with genetic susceptibility, cause the immune system to malfunction. Many factors may contribute to the disease, including exposure to certain viruses and bacteria.

Risk factors for rheumatoid arthritis

Several factors⁵ have been identified as increasing one’s risk of developing rheumatoid arthritis. These include:

• Age: The chances of developing rheumatoid arthritis increase as a person gets older. While rheumatoid arthritis can appear at any time, adults in their sixties⁶ are at the highest risk of developing the condition.

• Sex: Women are somewhere between 2 and 3 times more likely⁷ to develop rheumatoid arthritis than men.

• Genes: Rheumatoid arthritis appears to run in families. If one or more of your blood relatives have the disease, you may have a greater chance of developing it, too. There are specific genes that seem to be tied to rheumatoid arthritis, even though they are not the sole cause of the disease.

Additionally, having certain genes (specifically, HLA, or human leukocyte antigen) and class II genotypes can worsen rheumatoid arthritis in those who do develop it.

• Smoking: Smokers are at an increased risk of developing rheumatoid arthritis. Additionally, rheumatoid arthritis tends to be more severe in smokers than in nonsmokers with the disease.
• Obesity: People with higher BMIs (body mass indexes) tend to get rheumatoid arthritis more frequently. Some studies⁸ have found that the more overweight an individual is, the higher their chance of developing rheumatoid arthritis becomes. Obesity is particularly relevant to the development of rheumatoid arthritis in women aged 55⁹ or younger.

• Never having given birth: Having given birth to a live baby seems to offer some protection against developing rheumatoid arthritis. Women who have never given birth develop the condition at higher rates than those who have.
• Early life experiences: Exposure to certain toxins or experiences early in life may put a person at a higher risk of developing rheumatoid arthritis. For instance, rheumatoid arthritis is more common in individuals who grew up in lower-income households, while children with mothers who smoked may be up to twice¹⁰ as likely to develop the condition.

Rheumatoid arthritis symptoms

Because rheumatoid arthritis can affect many parts of the body, the extent and severity of symptoms can vary significantly between patients. Generally, however, most patients exhibit at least some (or all) of the following symptoms¹¹:

• Pain, aching, or tenderness in more than one joint
• Stiffness in more than one joint: This is usually worse in the mornings or after periods of not using the joint for a while (such as sitting for a long period of time)
• Swelling in more than one joint
• Bilateral symptoms: Most of the time, rheumatoid arthritis shows up in the same joints on both sides of the body (“mirrored” symptoms)
• Unexplained weight loss
• Fever
• Fatigue, tiredness, or exhaustion
• Weakness

Rheumatoid arthritis often shows up in smaller joints first (such as those in the wrists and hands), then progresses to larger joints over time. The disease’s symptoms may become severe, then appear to go away, then come back again. A period of symptoms that appear after a period of relief is referred to as a “flare” or “flare-up.” When symptoms go away again, a person is considered to be in remission.

In addition to the above symptoms, up to 40%¹² of patients with rheumatoid arthritis experience symptoms that are not related to their joints. These will look different depending on the patient, but most commonly show up in the:

• Skin
• Heart
• Lungs
• Eyes
• Salivary glands
• Bone marrow
• Blood vessels
• Nerve tissue

It can be difficult to determine which symptoms are related to rheumatoid arthritis and which ones stem from other causes or conditions. Arthritis specialists can usually recognize the symptoms of the disease and consider them holistically to form a comprehensive picture of how rheumatoid arthritis is affecting a particular patient.

Complications from rheumatoid arthritis

Because rheumatoid arthritis affects the entire body, it can lead to a number¹³ of health complications¹⁴, including:

• Osteoporosis: Rheumatoid arthritis can weaken the bones and make them more susceptible to breaks. Additionally, some of the medications used to treat rheumatoid arthritis can increase a patient’s chances of developing osteoporosis.
• Carpal tunnel syndrome: If rheumatoid arthritis causes inflammation in a person’s wrists, it can cause compression on the nerve that runs to the hands and fingers (the carpal tunnel). The numbness and tingling caused by carpal tunnel syndrome can be constant or can only occur during certain activities, such as typing or playing a musical instrument.
• Heart problems: Rheumatoid arthritis can cause the sac around the heart to become inflamed, eventually causing a variety of heart problems. It can also increase a patient’s risk of hardened and/or blocked arteries (atherosclerosis). Many times, these problems mimic heart issues that are usually only seen in older adults.
• Lung disease: Patients with rheumatoid arthritis can develop inflammation in their lungs, which eventually leads to scarring. As this scarring develops over time, it can lead to chronic shortness of breath. Certain medications prescribed for rheumatoid arthritis can also increase a patient’s risk of developing severe lung infections.
• Obesity: Rheumatoid arthritis can cause weight gain, which can lead to obesity (defined as having a BMI of 30.0 or higher). It can also cause an abnormally high fat-to-muscle ratio in patients who have a normal body mass index (between 18.5 and 24.9). This can lead to all of the complications associated with obesity.
• Rheumatoid nodules: These are firm bumps of tissue that appear under the skin. They often show up next to or near joints affected by the condition. They can also appear near pressure points or show up internally, such as inside the lungs.
• Dry eyes and mouth: Rheumatoid arthritis is frequently comorbid with Sjogren’s syndrome, which decreases the amount of moisture in both the mouth and the eyes. Patients with this syndrome may need to use eye drops or other treatments to keep their mucous membranes healthy.
• Lymphoma: People with rheumatoid arthritis are more likely to be diagnosed with lymphoma, a form of cancer that affects the lymphatic system.
• Increased risk of infections: Rheumatoid arthritis alone may cause an increased risk of developing certain infections, some of them severe. In addition, many of the medications prescribed for rheumatoid arthritis lower immune system functioning. People on these medications have an increased risk of developing infections. When they do develop infections, they may also find fighting them off to be more difficult than usual.

When rheumatoid arthritis is kept under control with the proper treatment, it’s possible to avoid many of these complications. Early detection is key to ensuring that rheumatoid arthritis does not progress to the point of causing severe symptoms or complications.