How does pannus tissue damage joints in rheumatoid arthritis?

In rheumatoid arthritis, pannus is a layer of roughened granulation tissue that develops as a result of chronic inflammation of the synovial membranes. This tissue contributes to joint damage through several destructive processes:1

• Cartilage Erosion: The pannus protrudes over the surface of the articular cartilage, causing the underlying cartilage to be eroded and destroyed.1
• Structural Replacement: Healthy joint structures, including the joint capsule and cartilage, are gradually replaced by this scarlike pannus tissue, leading to irreversible damage.1
• Ankylosis and Deformity: As the pannus thickens and hardens, it can cause the joints to become fixed in place, a condition known as ankylosis. Furthermore, this process often results in the displacement and physical deformity of the affected joints.1

Ultimately, the presence of pannus disrupts normal joint function, contributing to the progression of the disease from initial inflammation to potential crippling disability.1