Polyarthritis, Inflammatory, and Rheumatoid Arthritis

Untangling Confusing Terminology

Woman rubbing her arthritic hand
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Polyarthritis, inflammatory arthritis, and rheumatoid arthritis are an example of confusing medical terminology. The terms are often used interchangeably, but are they really synonymous? We know that there are many types of arthritis, so do the terms refer to three different types of arthritis? Let's consider each separately and determine the answer.

Polyarthritis

Polyarthritis refers to arthritis that affects more than four joints.

Polyarthritis usually results in polyarthralgia, which is defined as pain in more than four joints. Therefore, polyarthritis describes a pattern of joint involvement, but it is not a specific type of arthritis.  

Inflammatory Arthritis

Inflammatory arthritis typically affects several joints throughout the body simultaneously. It is caused by an overactive immune system, whereby the body attacks its own tissues (autoimmune disease), resulting in joint inflammation. Arthritis caused by inflammation is often associated with joint pain and stiffness, especially after periods of rest or inactivity (e.g., morning stiffness). There can be swelling, redness, and warmth around the affected joints, too. Inflammatory arthritis may also be associated with systemic effects. Rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis are types of inflammatory arthritis. Therefore, inflammatory arthritis literally refers to the inflammatory types of arthritis.

Simply put, it refers to types of arthritis that are associated with inflammation and active synovitis.

Rheumatoid Arthritis

Rheumatoid arthritis is a specific disease. It is a specific type of arthritis. It is a type of inflammatory polyarthritis. Rheumatoid arthritis is an autoimmune disease that typically involves many joints symmetrically (i.e., same joint on both sides of the body).

Rheumatoid arthritis may also be associated with systemic effects.

A Word From Verywell

Synonymous terms are equivalent in meaning. Based on that definition, polyarthritis, inflammatory arthritis, and rheumatoid arthritis are not synonymous—but they are definitely related. All three terms may appropriately be used to describe characteristics of rheumatoid arthritis. Rheumatoid arthritis is an inflammatory type of arthritis—quite possibly the best known and most common type of inflammatory arthritis. Rheumatoid arthritis can also be described as polyarthritis when more than 4 joints are affected.

Inflammatory arthritis does not exclusively refer to rheumatoid arthritis. As mentioned above, psoriatic arthritis, ankylosing spondylitis, and juvenile idiopathic arthritis are other inflammatory types of arthritis. The goal of treatment of inflammatory types of arthritis is to bring inflammation under control and to prevent permanent joint damage. The approach to treating inflammatory types of arthritis has shifted to be more aggressive than it was just two or three decades ago. Disease-modifying anti-rheumatic drugs (DMARDs) and biologic drugs are now typically part of the treatment regimen for inflammatory types of arthritis.

Methotrexate is the most commonly prescribed DMARD, and it can be used in combination with other DMARDs (e.g., triple therapy) or with the biologic drugs. 

To summarize, polyarthritis refers to the number of joints affected. Inflammatory arthritis refers to several types of arthritis that are associated with inflammation. Rheumatoid arthritis is a specific type of inflammatory arthritis.

Sources:

Primer on the Rheumatic Diseases. Arthritis Foundation. Thirteenth Edition.

Inflammatory Arthritis. Patient Education. Hospital for Special Surgery.

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