Arthritic hands, coloured gamma camera scan (scintigram). The hand most affected by the arthritis shows up darker on the scans. This is because the radioactive tracer injected to image the hands is taken up more by the inflamed area affected by the arthritis. Arthritis is a joint disease in which the joints become inflamed and painful. This is either because the body's immune system attacks them (rheumatoid arthritis) or through wear and tear (osteoarthritis).