5) Joint deformity
Another feature that differentiates rheumatoid arthritis from other types of joint pain is that the affected joints are deformed over time. Joint deformity in arthritis is caused by loss of cartilage, bone erosion, and ligament damage. Loss of cartilage causes joint ends to meet and triggers bone erosion, which is progressive and very severe in a later stage of the disease.
Joint deformity develops after a few years of having the disease when the inflammatory process is not controlled. However, patients may display mild deformity at the moment of the diagnosis. One of the most common is an ulnar deviation of the fingers in both hands.