There also are other, less common, forms of arthritis that can affect the shoulder. Septic arthritis can result from infection from bacteria, viruses or other microorganisms. It also is associated with rheumatoid arthritis. Avascular necrosis (osteonecrosis) develops when the blood supply to the bone is disrupted and the bone begins to die. Both forms of arthritis can result from injury, fracture, or other nontraumatic causes.