Which arthritic condition is classified as an autoimmune disorder?

Rheumatoid arthritis is classified as an autoimmune disorder because the body's immune system mistakenly attacks its own joint tissues. This leads to inflammation, pain, swelling, and stiffness in the joints. Unlike other types of arthritis, such as osteoarthritis, which is primarily a wear-and-tear condition, rheumatoid arthritis involves an abnormal immune response that disrupts the normal functioning of the joints and can even affect other organs. This characteristic of being driven by the immune system's malfunction is what distinctly categorizes rheumatoid arthritis as an autoimmune condition.

Other types of arthritis, such as osteoarthritis and post-traumatic arthritis, are not autoimmune disorders; they result from mechanical wear and tear on the joints or injury. Gout is a type of arthritis caused by the buildup of uric acid crystals in the joints, and it also does not fit into the autoimmune category. Therefore, rheumatoid arthritis stands out as the correct answer due to its underlying autoimmune nature.