Common sites for pannus formation include over the cornea, over a joint surface (as seen in rheumatoid arthritis), or on a prosthetic heart valve.
[1] Pannus may grow in a tumor-like fashion, as in joints where it may erode articular cartilage and bone.
Chronic inflammation and exuberant proliferation of the synovium leads to formation of pannus and destruction of cartilage, bone, tendons, ligaments, and blood vessels.
[3] In people suffering from rheumatoid arthritis, pannus tissue eventually forms in the joint affected by the disease, causing bony erosion and cartilage loss via release of IL-1, prostaglandins, and substance P by macrophages.
Chronic local hypoxia (such as that occurring with overuse of contact lenses) or inflammation may lead to peripheral corneal vascularization, or pannus.