Rheumatoid Arthritis Glossary

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The purpose of this rheumatoid arthritis (RA) glossary is to define and explain the meaning of many words and terms related to this potentially debilitating type of arthritis. Having a basic knowledge about adult RA and juvenile idiopathic arthritis (JIA)—the form of RA affecting children—can help improve your understanding of your symptoms, doctor’s diagnosis and treatment options.Arthritis affects many areas of the body, various slides.Having a basic knowledge about adult RA and juvenile idiopathic arthritis can help improve your understanding of your symptoms, doctor’s diagnosis and treatment options. Photo Source: 123RF.com.


Low red blood cell count. A symptom of rheumatoid arthritis (RA).

Anti-TNF (Tumor Necrosis Factor) Drugs (TNF Inhibitors)
Drugs that block the action of tumor necrosis factor, a protein that promotes inflammation. An example of a TNF inhibitor is adalimumab (Humira).

Atlanto-axial Joint
The joint space between the atlas (C1, the first vertebra of your cervical spine or neck) and the axis (C2, the second vertebra of your cervical spine). This joint is commonly affected by rheumatoid arthritis in the spine.

Autoimmune Disease

When the body’s immune system cannot tell the difference between a healthy cell or a diseased cell. When healthy, the body's immune system produces antibodies to fight infection and disease. But in autoimmune disease, the body attacks itself. Rheumatoid arthritis is an autoimmune disease.

B Cell
A type of white blood cell involved in rheumatoid arthritis. B cells release antibodies (immune proteins) when T cells produce of cytokines. When B cells release antibodies, it causes inflammation.

Prescription medications that reduce inflammation and slow joint damage.

Disease-modifying Anti-rheumatic Drugs (DMARDs)
Medications that work slowly to "modify" rheumatoid arthritis. It can take several months before you notice any benefit. These drugs may slow disease progression and preserve joint tissue. Methotrexate (Rheumatrex) is an example of a DMARD.


Fluid retention. A symptom of RA.

Facet Joints

A joint is the meeting point of 2 or more bones, and it allows the bones to move. Spinal joints are called facet joints (or zygapophyseal joints). Facet joints help stabilize the spine and assist in preventing excessive spinal movement. However, the spine may become unstable when rheumatoid arthritis affects the facet joints.


When RA symptoms are active or worsen.

Human Leukocyte Antigens (HLAS)

Genetic markers believed to play a role in rheumatoid arthritis. People with those markers have 5 times the risk for developing RA than those without them; they also may have a more severe course of the disease. The genetic marker, HLA-DR4, in particular, is often present in people with RA. However, the presence of this genetic marker doesn't guarantee the development of RA.

Immune System

The body’s defense against antigens (ie, foreign invaders), which include different types of bacteria, viruses, and toxins. To rid the body of antigens, the immune system triggers an inflammatory response.

Janus Kinase Inhibitors (JAK)

A class of medication that acts on JAK pathways involved in the immune response in the body. Tofacitinib citrate (Xeljanz) is an example of this type of drug.


Response to a stimulus (such as a nerve signal) to a muscle, causing it to contract.


A diagnostic test to identify spinal cord disorders. The subarachnoid space of the spinal cord is injected with a contrast medium (a dye), followed by x-rays, CT, or MRI scans. A myelogram can help the doctor see areas of nerve compression around the spinal canal and cord.


Disturbance (eg, compression) of the spinal cord.

Non-steroidal Anti-inflammatory Drugs (NSAIDs)

Medications that can relieve RA inflammation and pain. Available over-the-counter or by prescription. Ibuprofen (Aleve) is an example of a NSAID.

Non-TNF Biologics

A newer generation of drug treatment for RA. These drugs are given injection or infusion. Abatacept (Orencia) is an example.

Odontoid Process

Also called the dens, the odontoid process is a bony, peg-like projection that extends up from the axis (C2) to the atlas (C1) in your cervical spine. It helps your head to nod and turn side-to-side.


A bony overgrowth. Also called a bone spur.


An abnormal sensation, such as tingling, burning, or pins and needles.


A slight to moderate degree of paralysis in the lower extremities.


When RA symptoms improve.

Rheumatoid Arthritis

Also called RA, it is the most debilitating type of arthritis. RA can cause joint deformity and may lead to physical disabilities.

Rheumatoid Factor

A normal component in blood. About 80% of patients with RA have higher blood levels of rheumatoid factor (RF), a group of antibodies that accumulate in the synovium.

Rheumatoid Nodules

Small bumps beneath the skin, especially near the elbows. A symptom of RA.


A medical doctor who specializes in autoimmune conditions (rheumatic diseases) that reduce joint, muscle, and bone function.


Relating to sensation: feeling, pressure, temperature.


When a patient’s blood (sero or serum) is positive for the rheumatoid factor. However, not everyone with RA is seropositive, and people who don’t have rheumatoid arthritis can also be seropositive.

Spinal Instrumentation and Fusion

Surgical treatment for RA. Spinal fusion fuses 2 or more vertebrae affected by RA into 1 solid bone by using instrumentation and bone graft. The goal is to correct spinal deformity and provide permanent stability to the spinal column.


An incomplete dislocation or altered contact between joint surfaces.


A thin membrane inside the joint capsule. Synovial fluid lubricates the joint, enabling healthy movement, and nourishes the joint. RA attacks joint synovium.

T Cell

A types of white blood cell involved in rheumatoid arthritis. T cells release cytokines (chemicals that play a role in the inflammatory response) that trigger a response from B cells, leading to inflammation.

Vertebral End Plates

The upper and lower plates of the vertebral body adjacent to the intervertebral disc.

Updated on: 03/15/19
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What Is Rheumatoid Arthritis?
Lawrence G. Lenke, MD
Professor of Orthopedic Surgery
Columbia University Medical Center
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What Is Rheumatoid Arthritis?

Rheumatoid arthritis (RA) is the most debilitating type of arthritis because it can cause deformity and disability. RA may affect the cervical spine and cause the facet joints in the neck to become inflamed and painful.
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