Polyarthritis, Inflammatory, and Rheumatoid Arthritis

Polyarthritis, inflammatory arthritis, and rheumatoid arthritis are an example of confusing medical terminology. The terms are often used interchangeably, but are they really synonymous or do they refer to three different types of arthritis? Let's consider each separately so you can fully understand how these terms are related and what they mean when you see them in discussions of arthritis.

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. Rheumatoid arthritis can be referred to as a type of polyarthritis when four or more joints are involved. Other conditions that can produce polyarthritis include psoriatic arthritis,  amyloidosis, lupus, scleroderma,  juvenile idiopathic arthritis, alphaviral infections. It can also be a transient symptom as part of an acute illness such as in rheumatic fever.

Inflammatory arthritis typically affects several joints throughout the body simultaneously. It is caused by an autoimmune disease in which an overactive immune system attacks the body's own tissues. This action results in joint inflammation.

Arthritis caused by inflammation is often associated with joint pain and stiffness, especially after periods of rest or inactivity, such as in morning stiffness. There can be swelling, redness, and warmth around the affected joints.

Inflammatory arthritis may also be associated with systemic effects. Rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis are types of inflammatory arthritis. Simply put, it refers to types of arthritis that are associated with inflammation and active synovitis.

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. TNF blockers, one of the types of biologic drugs, effectively reduce chronic inflammation in people with rheumatoid arthritis, decrease mortality, and reduce the risk of cardiovascular events.

Rheumatoid arthritis is a specific disease and it is a type of inflammatory polyarthritis, so all three terms apply to it. Rheumatoid arthritis is an autoimmune disease that typically involves many joints symmetrically, affecting the same joint on both sides of the body. Rheumatoid arthritis may also be associated with systemic effects. Early and aggressive treatment of rheumatoid arthritis can help prevent joint damage from the inflammation.

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.