The exact causes of the inflammatory rheumatoid arthritis that causes swelling and deformity in the fingers are unknown, but osteoarthritis is known to be caused by the wearing away of the protective cartilage between joints, according to WebMD. Both forms of arthritis can result in structural changes and deformity.
Rheumatoid arthritis, or RA, is a painful autoimmune disease that causes the destruction of the synovial tissue, or the cells that act as lubricants for the joints, explains WebMD. The stiffness, pain, swelling and deformity are typically found in the same joints on both sides of the body. Often the affected individual experiences persistent fatigue and symptoms similar to that of the flu. Women suffer with rheumatoid arthritis in far greater numbers than men. A viral or bacterial infection may cause RA, and there may be a genetic predisposition to the disease.
Osteoarthritis, or degenerative arthritis, is the most common form of arthritis, according to WebMD. The condition can affect any joint but most commonly it is seen in the hands, feet, hips and knees. As the cushioning cartilage progressively wears away, the bones in the fingers rub against each other, causing limited dexterity and loss of function and strength in the hands. Age is the primary precursor to osteoarthritis, but individuals who have sustained severe injuries to specific joints or those with professions that cause repeated stress on specific joints, are at higher risk.