There is no proper explanation why our immune system attacks our own joint tissue. Studies have however shown when RA can develop. A combination of genes and exposure to environmental factors starts the development of RA.

• Before symptoms occur, the immune system might have been triggered or activated years before.
• The autoimmune process may happen in other areas of the body, but the impact of the immune malfunction settles in the joints.
• Immune cells cause inflammation in the inner lining of the joint, called the synovium.
• This inflammation becomes chronic, and the synovium thickens due to an increase of cells, production of proteins, and other factors in the joint, which can lead to pain, redness, and warmth.
• As RA progresses, the thickened and inflamed synovium pushes further into the joint and destroys the cartilage and bone within the joint.
• The surrounding muscles, ligaments, and tendons that support and stabilize the joint become weak over time and do not work as well. This can lead to more pain and joint damage and limits mobility.