Final answer:
Arthritis is the most common inflammatory disorder in the United States, with rheumatoid arthritis being the most prevalent form of chronic inflammatory joint disease.
Step-by-step explanation:
The most common inflammatory disorder in the United States is arthritis. Arthritis is a disorder that results in significant joint pain, swelling, stiffness, and reduced joint mobility. There are over 100 different forms of arthritis, but the most common chronic inflammatory joint disease is rheumatoid arthritis (RA). RA involves immune reactions leading to chronic inflammation, mainly affecting the joints like hands, feet, and legs.