rheumatoid arthritis
Meaning of rheumatoid arthritis: Stiffness that is worst on waking and eases with movement is the pattern separating it from ordinary wear on a joint.
Definition of rheumatoid arthritis
Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the synovium, the thin membrane lining the joints. The lining thickens and inflames, causing pain, swelling and prolonged morning stiffness, and the inflamed tissue gradually erodes cartilage and bone. It usually involves small joints on both sides of the body at once.
How does it differ from osteoarthritis?
Both cause painful joints, and they are otherwise almost opposite conditions.
| Feature | Rheumatoid arthritis | Osteoarthritis |
|---|---|---|
| Underlying process | Immune attack on the joint lining | Failure of cartilage to withstand and repair mechanical load |
| Joints affected | Knuckles, middle finger joints, wrists and the balls of the feet, usually matching on both sides | Knees, hips, spine and the joints nearest the fingertips, often unevenly |
| Stiffness | Worst on waking, lasting an hour or more, easing with movement | Brief on waking, worse after use through the day |
| Reach beyond the joint | A whole body illness with fatigue and effects on other organs | Confined to the affected joints |
What happens inside the joint?
The synovium is normally a delicate membrane a few cells thick that produces the fluid lubricating the joint. Under immune attack it swells into thickened, inflamed tissue crowded with immune cells, and that mass creeps across the joint surface. Enzymes released from it dissolve cartilage and then bite into the bone at the joint margin, producing the erosions visible on imaging. Lost cartilage and eroded bone do not regenerate, so damage accumulates, which is why the tempo of treatment matters more in this arthritis than in most.
What happens outside the joints?
Because it is a systemic autoimmune disease, effects reach well beyond the hands. Firm nodules can form under the skin over pressure points. The lungs can develop inflammation and scarring, the eyes can become dry or inflamed, the membrane around the heart can be involved, and long standing inflammation lowers red cell production and raises cardiovascular risk. Fatigue is often the symptom people rate as most limiting. Two antibodies in the blood support recognition of the disease, one of them considerably more specific than the other, though neither is present in every case, and the pattern of joints involved together with imaging carries as much weight as either.
Also known as
Used in a sentence
The patient was referred to rheumatology for evaluation of symmetric joint swelling suggestive of rheumatoid arthritis.
Good to know
Rheumatoid arthritis is distinguished from osteoarthritis by its autoimmune, inflammatory basis and its tendency to affect joints symmetrically, whereas osteoarthritis relates to mechanical wear and more often affects joints asymmetrically.
Word origin
Where “rheumatoid arthritis” comes from
Formed from rheumatoid, from Greek rheuma, meaning flow or discharge, and -oid, meaning resembling, and arthritis, from Greek arthro-, meaning joint, and -itis, meaning inflammation.