What Is Inflammation?
Inflammation plays a role in arthritis, but it differs depending on the type of arthritis.
Your achy joint that’s swollen and feels stiff is probably harboring inflammation. If you have arthritis (whether osteoarthritis or rheumatoid arthritis), inflammation contributes to pain and other symptoms. Many drugs for arthritis work by reducing inflammation. But what is inflammation?
Inflammation actually is a natural response of the body to protect itself from harm. “It has a positive role because the body is trying to heal itself,” says Cleveland Clinic orthopaedic specialist Vikas Patel, DO.
Observe what happens when you cut yourself. Very quickly, the area becomes red, swollen and tender. This happens because the immune system has dispatched specialized inflammatory mediators that promote healing. They cause blood vessels to dilate to allow more blood, which carries healing cells, to reach the area (causing redness).
The area becomes swollen so more defense cells can act at the site. The goal is to remove harmful substances, such as bacteria, damaged cells and other debris. Some mediators activate the pain cascade. This discourages you from using injured tissue until it has healed.
With an acute injury or infection, this process is a good thing. Once healing is complete, the inflammatory response is turned off and everything goes back to normal. However, inflammation that becomes chronic switches from being good to being harmful. This is the case with many forms of arthritis.
With osteoarthritis, the cushioning material that covers the ends of bones at joints (called cartilage) wears down. As this happens, the cells that make up cartilage (called chondrocytes) die off. This triggers the immune system’s inflammatory response.
“The body sends in inflammatory mediators to try to repair cartilage, but cartilage cannot be repaired,” says Dr. Patel. So you get the redness, swelling and pain of an inflammatory response, but the cartilage never heals.
“Inflammation plays a large role in the pain from osteoarthritis, but it’s not the only source of pain,” says Dr. Patel. Other mechanical and degenerative factors can also contribute.
Anti-inflammatory drugs—both nonsteroidal ones (NSAIDs) and steroids (also called corticosteroids)—can be effective because they reduce the production of chemicals involved in the inflammatory process. NSAIDs block the enzyme COX-2, which prevents inflammatory substances called cytokines from becoming active. The result is less inflammation and less pain. (NSAIDs have other effects, which is why they may lead to side effects and risks when taken long term.)
Because osteoarthritis originates from a degenerative process, NSAIDs and corticosteroids don’t reverse it or prevent it from worsening. They only provide temporary relief of symptoms.
Rheumatoid arthritis is an autoimmune disease, and the inflammatory process works differently than with osteoarthritis. The body’s immune system mistakenly identifies normal tissue in joints (and elsewhere in the body) as harmful and attacks with an inflammatory response, which damages healthy joints.
The main treatment for rheumatoid arthritis involves drugs that suppress different parts of the body’s immune system response. They are called disease-modifying antirheumatic drugs (DMARDs) because they slow down the worsening of the disease.
“The effects of DMARDs for rheumatoid arthritis are profound because they block the inflammatory mediators responsible for the disease,” Dr. Patel explains. Common DMARDs include methotrexate and the biologic drugs infliximab (Remicade®), adalimumab (Humira®) and etanercept (Enbrel®).