Reviewed by: HU Medical Review Board | Last reviewed: January 2021 | Last updated: April 2021

The job of your immune system is to fight germs and diseases. When infection, injury, or illness begins to damage the body, your immune system fights back by sending healing cells. These cells release chemicals that make your blood vessels dilate (open wide).1

When your blood vessels open wide, they allow more blood to get to the damaged area, bringing more healing cells. The increased blood flow causes redness and heat to the damaged area. Extra healing cells and fluid go to the damaged area, leading to swelling. The swelling causes pain in the area.1

Why does inflammation happen?

Inflammation is a normal process and allows your body to heal from injury or illness. However, if inflammation continues, chronic inflammation can occur. Chronic inflammation may last months to years and can lead to damage within the body.1

Rheumatoid arthritis (RA) is an autoimmune condition where the body mistakenly attacks its healthy tissues inside the joints. Inflammation is a key feature of RA and is responsible for the pain and swelling of joints associated with pain and swelling of joints. This inflammation may also impact your heart, blood vessels, lungs, and eyes.2

Which joints are affected?

Joint pain, swelling, tightness, and stiffness are the most common symptoms of RA. Joints in the hands, wrists, feet, and knees are usually affected first. Over time, RA may affect other joints, including the shoulders, hips, and elbows.3,4

In some cases, RA affects many joints at the same time on both sides of the body. Joint stiffness is usually worse after resting the joint, especially in the morning.3,4

In the early stages of RA, small joints tend to be affected more than large joints. For instance, the joints located at the base of the fingers and toes, and the joints located in the middle of the fingers may be more affected. In some people, RA may begin with pain in a large joint (shoulder or knee) that moves from 1 joint to another and comes and goes.3

When does RA-related inflammation occur?

With RA, inflammation can occur at any time. Most people with RA experience periods when the disease worsens beyond normal day-to-day variations and is more active. These periods of worsening condition are called flares, during which inflammation and associated symptoms (swelling, pain, stiffness) may be more severe.5

Areas affects beyond the joints

RA inflammation does not stop at the joints. Extra-articular (outside the joints) symptoms also occur in RA.


RA nodules are flesh-colored lumps or masses that typically develop under the skin (subcutaneously). RA nodules typically form in areas subject to pressure including the elbows, finger joints, wrist, hip, lower back, and Achilles tendon. Doctors think that these nodules form in response to inflammation. Rheumatoid nodules occur in up to 1 in every 4 people with RA.6


RA is associated with a variety of conditions involving inflammation of the lungs and related tissues:7-9

  • Pleurisy (pleuritis) is the inflammation of the 2 layers of tissue surrounding the lungs and separates the lungs from the chest wall. These layers are called the pleura. With pleurisy, every time your lungs expand when you breathe, the pleura “stick” together like sandpaper, causing sharp pain.
  • Pulmonary fibrosis is the formation of fibrous tissue inside the lungs that appears on an X-ray as scarring. Up to 40 percent of people with RA develop pulmonary fibrosis. The formation of scar tissue interferes with the ability of the lung to expand normally upon inhalation. It can lead to chest discomfort, shortness of breath, fatigue, weakness, and a chronic cough.
  • Interstitial lung disease (ILD) includes a range of conditions that inflame and scar the tissues of the lungs. When the scarring builds over time, breathing becomes more difficult. About 1 in 10 people with RA develop ILD. ILD may require a lung transplant to breathe adequately.

Heart and blood vessels

Pericarditis, or inflammation of the layer around the heart, may occur with RA. Symptoms of pericarditis include sudden chest pain and difficulty breathing.10

Vasculitis, inflammation of the blood vessels, can affect blood vessels throughout the body. This complication is rare but may result in ulcers in the legs and a rash on the skin caused by bleeding from small blood vessels.11


Inflammation in RA may affect nerve function and result in tingling, pain, or numbness, known as neuropathy.12

Eyes and mouth

RA inflammation is linked to secondary Sjögren’s syndrome, an autoimmune disease in which inflammation affects the glands that produce tears and saliva. Secondary Sjogren’s syndrome results in a decrease in the production of tears and saliva.13,14

Additionally, RA inflammation can lead to episcleritis, affecting the white part of the eye and causing pain, light sensitivity, and tearing.13,14

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