How can rheumatoid arthritis lead to ankylosis and loss of joint movement?

In rheumatoid arthritis, the process leading to ankylosis and the loss of joint movement begins with chronic inflammation of the synovial membranes. This inflammation causes the lining of the joint to thicken and form a layer of roughened granulation tissue known as pannus.12

As the disease progresses, this pannus protrudes over the surface of the cartilage, leading to its erosion and destruction. When the injury is severe, large areas of bone may be denuded of cartilage, causing adhesions to form between the articular surfaces. These adhesions eventually transform into mature fibrous or bony connective tissue, resulting in a firm union between the bony surfaces—a condition defined as ankylosis. This fusion effectively fixes the joint in place, which interferes with normal motion and can render the joint totally immobile. Additionally, the destruction of supporting structures like tendons and ligaments can further contribute to joint instability and deformity.1342