What autoimmune disease primarily attacks the joints?

Rheumatoid arthritis is the autoimmune disease that primarily attacks the joints.

In rheumatoid arthritis, the immune system mistakenly targets the synovium, the lining surrounding movable joints. This causes persistent inflammation, swelling, warmth, pain, and stiffness—often worse after rest or in the morning. The wrists, hands, feet, and cervical spine are commonly affected, and the pattern is frequently symmetrical.

The inflammation can gradually damage cartilage, bone, tendons, and ligaments, potentially causing deformity and loss of movement. Rheumatoid arthritis is also systemic: it can affect the lungs, heart, eyes, skin, nerves, and blood. Its exact cause is unknown, but genetic susceptibility and environmental factors such as smoking both contribute. Augustin Jacob Landré-Beauvais published an early clinical description in 1800.

A common mix-up is osteoarthritis, which is primarily a degenerative joint disorder rather than an autoimmune disease. Lupus can also cause inflammatory joint symptoms, but it is a broader systemic autoimmune disease, not the single canonical answer to this question.