Rheumatoid arthritis symptoms are caused by inflammation. That means your body’s immune system is releasing chemicals into your blood and joints that cause pain, swelling, stiffness, and fatigue. Why? Because when you have RA, the normal signals that tell your immune system to spring into action — to protect your body from harm by viruses, bacteria, or injuries — are crossed. That’s called autoimmunity. In an autoimmune disease like RA, your immune system triggers inflammation and attacks your healthy joints and tissues by mistake. That’s why you have pain, swelling, and other symptoms.
Sometimes you feel like your immune system is constantly attacking your body; at other times symptoms will come and go. As a reminder, RA is different than OA (osteoarthritis), which is caused by mechanical wear and tear on joints, not an autoimmune process. However, both types of arthritis may occur at the same time.
Even over just a few months or years, RA inflammation can do a lot of damage to the lining around your joints, called the synovium. This inflamed lining can cause damage to the tissues around your joint, like your cartilage or ligaments that hold the joint together. When your cartilage breaks down, your bones can rub against each other and cause more pain. If your ligaments tear, your joints may dislocate and later become deformed. If that happens, joints can look twisted or gnarled, and be harder to move.