What is the main characteristic of rheumatoid arthritis?

The main characteristic of rheumatoid arthritis is chronic inflammation of joints. This autoimmune condition is fundamentally marked by persistent inflammation of the synovial membranes, which line the joints. This inflammation can lead to various symptoms, including joint pain, swelling, and stiffness, and can potentially result in joint destruction if not adequately managed.

In rheumatoid arthritis, the inflammation is systemic and affects multiple joints, often in a symmetrical fashion, distinguishing it from other types of arthritis such as osteoarthritis, which is primarily degenerative. This chronic inflammation can also lead to extra-articular manifestations, affecting other systems in the body.

The other options highlight features that are either not characteristic of rheumatoid arthritis or represent different conditions. Joint laxity is more associated with conditions affecting the connective tissues or disorders that lead to hypermobility, while localized swelling in one joint might suggest an acute process or another type of arthritis. Degeneration of cartilage occurs in various forms of arthritis, particularly osteoarthritis, but is not the primary feature in rheumatoid arthritis, which is more about inflammation than just cartilage degeneration.