Rheumatology Glossary

A to C

Anti-CCP — An antibody test used in diagnosing rheumatoid arthritis. It is more specific than rheumatoid factor, meaning a positive result points more firmly to the disease, though a negative result does not exclude it.

ANA — Antinuclear antibody. A screening test for autoimmune connective tissue disease. Up to 15 percent of healthy adults test positive, so it is interpreted alongside symptoms rather than on its own.

Ankylosing spondylitis — A form of inflammatory arthritis affecting mainly the spine and the sacroiliac joints. Now usually described as part of axial spondyloarthritis.

Arthralgia — Joint pain without demonstrable swelling. Distinct from arthritis, which involves inflammation you can see or feel.

Arthritis — Inflammation of a joint. An umbrella term covering more than a hundred conditions, from osteoarthritis to rheumatoid arthritis, which are treated very differently.

Autoantibody — An antibody that targets the body's own tissues rather than an infection. Their presence and pattern help identify which autoimmune disease is present.

Axial spondyloarthritis — Inflammatory disease of the spine and sacroiliac joints, causing back pain that is worse on waking and better with movement. Often diagnosed years late.

Biologic — A treatment made from living cells that blocks one specific part of the immune response. Given by injection or infusion, and usually supplied through a specialty pharmacy.

Biosimilar — A close copy of a biologic, approved after the original patent expires. Held to rigorous equivalence standards and usually considerably cheaper.

Bone density scan — See DEXA.

Connective tissue disease — A group of autoimmune diseases including lupus, Sjogren's disease, scleroderma and myositis, which affect tissues throughout the body rather than joints alone.

CRP — C-reactive protein. A blood marker of inflammation that rises and falls quickly, making it useful for tracking disease activity. It can be normal in active early disease.

Crystal arthritis — Joint inflammation caused by crystals forming in the joint. Gout involves uric acid crystals; pseudogout involves calcium pyrophosphate crystals.

Illustrative photograph, included as a visual reference rather than a depiction of this practice.

D to I

DEXA — Dual-energy X-ray absorptiometry. The scan that measures bone density to diagnose osteoporosis. It takes about ten to fifteen minutes and uses less radiation than a chest X-ray.

DMARD — Disease-modifying antirheumatic drug. A treatment that slows the disease itself rather than only relieving symptoms. Methotrexate is the most widely used.

Enthesitis — Inflammation where a tendon or ligament attaches to bone, commonly at the heel. Characteristic of psoriatic arthritis and axial spondyloarthritis.

Erosion — Loss of bone at the edge of a joint, visible on imaging, caused by persistent inflammation. Erosions do not reverse, which is why early treatment matters.

ESR — Erythrocyte sedimentation rate. An older marker of inflammation that responds more slowly than CRP and is affected by age, sex and anaemia.

Fibromyalgia — A condition of widespread pain, fatigue and unrefreshing sleep without joint inflammation. It can coexist with inflammatory disease, which complicates assessment.

Flare — A period when disease activity increases. Distinguishing a genuine flare from mechanical pain or a coexisting problem is a routine part of follow-up.

Giant cell arteritis — Inflammation of medium and large arteries, usually over the age of 50. Causes headache, scalp tenderness and jaw pain, and can cause permanent blindness, so it is treated on suspicion.

Gout — Arthritis caused by uric acid crystals, classically affecting the base of the big toe. Highly treatable, and one of the few rheumatic diseases where attacks can be stopped almost entirely.

Hydroxychloroquine — A long-established treatment for lupus and mild rheumatoid arthritis, generally well tolerated, requiring periodic eye checks with long-term use.

Immunosuppressant — A medicine that reduces immune activity in order to control autoimmune disease. Effective, and the reason infection risk is monitored.

Inflammation — The immune response causing swelling, warmth, redness and pain. Useful against infection; damaging when directed at the body's own tissues.

Inflammatory back pain — Back pain that is worse after rest, better with movement, stiff on waking and often wakes you in the second half of the night. The opposite pattern to mechanical back pain.

J to R

JAK inhibitor — A tablet that blocks a specific internal signalling pathway in immune cells. An alternative to injected biologics for some conditions, with its own monitoring requirements.

Lupus — Systemic lupus erythematosus. An autoimmune disease that can affect skin, joints, kidneys, blood and other organs, and which varies enormously between individuals.

Methotrexate — The most widely used disease-modifying drug in rheumatology. Taken weekly, never daily, alongside folic acid, with regular blood monitoring.

Monoarthritis — Inflammation in a single joint. When it is hot, very swollen and painful with fever, infection must be excluded urgently.

Myositis — Inflammation of muscle causing weakness, typically difficulty rising from a chair or lifting the arms above the head.

NSAID — Non-steroidal anti-inflammatory drug, such as ibuprofen or naproxen. Relieves pain and inflammation but does not modify disease, and carries stomach, kidney and cardiovascular considerations.

Osteoarthritis — Joint disease driven by cartilage wear rather than autoimmune inflammation. The most common form of arthritis, and managed quite differently from inflammatory arthritis.

Osteoporosis — Loss of bone density leading to fractures from minor falls. Entirely silent until a bone breaks, which is why screening matters.

Polyarthritis — Inflammation involving five or more joints, a pattern that points towards rheumatoid arthritis and related diseases.

Polymyalgia rheumatica — Sudden aching and stiffness across the shoulders, neck and hips in people over 50. Responds rapidly to treatment and can accompany giant cell arteritis.

Prednisone — An oral steroid that reduces inflammation quickly. Valuable in the short term; used at the lowest effective dose because of longer-term effects on bone, glucose and weight.

Prior authorization — Approval from an insurer for a specific medicine or scan before it can be provided. Common for biologics and MRI.

Psoriatic arthritis — Inflammatory arthritis associated with psoriasis, which can affect joints, spine, tendon insertions and nails. The skin disease may be mild or hidden.

Raynaud's phenomenon — Fingers or toes turning white then blue in the cold before flushing red. Often harmless in isolation, but can accompany connective tissue disease.

Remission — Disease activity reduced to a minimum, with no swollen joints and normal inflammatory markers. The goal of treatment in inflammatory arthritis.

Rheumatoid factor — An antibody found in most but not all people with rheumatoid arthritis. Also present in other conditions and in some healthy people, so it is not diagnostic on its own.

S to Z

Sacroiliac joints — The joints between the base of the spine and the pelvis. Inflammation here is a defining feature of axial spondyloarthritis and is best seen on MRI.

Scleroderma — An autoimmune condition causing thickening and hardening of skin and sometimes internal organs. Ranges from limited skin involvement to systemic disease.

Septic arthritis — Infection inside a joint. A medical emergency that can destroy a joint within days, presenting as a single hot, very swollen, severely painful joint, often with fever.

Seronegative — Having the disease without the usual antibodies. Around one in five people with rheumatoid arthritis are seronegative, which is why normal blood tests do not exclude it.

Sjogren's disease — An autoimmune condition causing persistent dryness of eyes and mouth, often with fatigue and joint pain.

Specialty pharmacy — A pharmacy that dispenses biologics and other complex medicines, usually delivering to your home. Most plans require a specific one.

Steroid-sparing — Using a disease-modifying drug so that steroid doses can be reduced or stopped. A standard aim in long-term management.

Step therapy — An insurer requirement to try cheaper treatments first and document that they failed before approving a more expensive one. A coverage rule rather than a clinical one.

Synovitis — Inflammation of the joint lining. What a rheumatologist is feeling for when examining a joint, and what distinguishes a swollen joint from a merely painful one.

Systemic — Affecting the body as a whole rather than one site. Systemic disease may involve skin, blood, kidneys or lungs alongside joints.

Tender joint count — The number of joints painful on examination. Combined with the swollen joint count and blood markers to produce a disease activity score.

Titre — The concentration of an antibody, reported as a ratio such as 1:80 or 1:1280. The number matters: a high ANA titre carries very different weight from a borderline one.

Uric acid — The waste product that forms gout crystals. Treatment aims to lower it below a target level rather than simply into the normal range.

Uveitis — Inflammation inside the eye, which can accompany axial spondyloarthritis and psoriatic arthritis. Painful red eye with light sensitivity needs same-day assessment.

Vasculitis — Inflammation of blood vessels, which can restrict blood supply to skin, nerves or organs. A group of conditions ranging from mild to life-threatening.

PLACEHOLDER: these definitions are written for patients and deliberately simplified. They require physician review before launch to confirm that no simplification has become inaccurate.