Bilateral x-ray of the hands and wrists of a 54 year old patient with rheumatoid arthritis. The scan shows fusing carpometocarpal arthritis of the right hand and bone erosion of the left proximal interphalangeal joint. Rheumatoid arthritis is a degenerative autoimmune disease that mainly affects the capsule (synovium) around the synovial (flexible) joints, causing chronic inflammation. It can be a debilitating and painful condition and can lead to deformities and loss of functioning and mobility.