Ankylosing spondylitis - a type of arthritis that affects the spine.
Antibody - a special protein produced by the body's immune system that recognizes and helps fight infectious agents and other foreign substances that invade the body.
Arthralgia - pain in the joint.
Arthritis - inflammation of the joint.
Arthroscopy - the use of an intra-articular camera inserted into the joint through a small incision to show the inside of a joint; the procedure allows the physician to also assess, repair, or reconstruct various tissues both within and around joints.
Bursa - fluid-filled sacs between bones and ligaments, or other adjacent structures.
Bursitis - inflammation of the bursa.
Cartilage - a connective tissue that covers the ends of bones in a joint.
Computed tomography scan (also called a CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.
Dermatomyositis - a type of rheumatic disease in which the blood vessels under the skin and muscles are inflamed, causing damage to the muscle tissue.
Electrocardiogram (ECG or EKG) - a test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias), and detects heart muscle damage.
Electromyogram (EMG) - a test that measures the electrical activity of a muscle or a group of muscles. An EMG can detect abnormal electrical muscle activity due to diseases and neuromuscular conditions.
Erythrocyte sedimentation rate (ESR) - a measurement of how quickly red blood cells fall to the bottom of a test tube. When swelling and inflammation are present, the blood's proteins clump together and become heavier than normal. Thus, when measured, they fall and settle faster at the bottom of the test tube. Generally, the faster the blood cells fall, the more severe the inflammation.
Fibromyalgia (also called fibrositis) - chronic, widespread pain in muscles and soft tissues surrounding joints, accompanied by fatigue.
Henoch-Schönlein purpura (HSP) - a form of vasculitis, a condition which involves inflammation of the blood vessels. The most common vasculitis in children along with Kawasaki disease.
Immune system - a collection of cells and proteins that works to protect the body from potentially harmful, infectious microorganisms, such as bacteria, viruses, and fungi.
Joint - where two bones meet.
Juvenile rheumatoid arthritis (JRA) - a form of arthritis in children ages 16 or younger that causes inflammation and stiffness of the joints.
Kawasaki disease (also called mucocutaneous lymph node syndrome) - the most common form of vasculitis that primary affects children, along with HSP (Henoch-Schönlein purpura), that commonly affects children. The disease produces irritation and inflammation of many tissues of the body, including the hands, feet, whites of the eyes, mouth, lips, and throat.
Ligaments - a white, shiny, flexible band of fibrous tissue that binds joints together and connects various bones and cartilage.
Magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
Musculoskeletal system - the complex system that include: bones, joints, ligaments, tendons, muscles, and nerves.
Nodule - bump.
Patella - the knee-cap.
Pauciarticular - a form of juvenile rheumatoid arthritis that affects four or less joints.
Pericarditis - inflamed sac around the heart.
Pleurisy - inflamed membranes around the lungs.
Polyarticular - a form of juvenile rheumatoid arthritis that affects five or more joints.
Psoriatic arthritis - a form of arthritis associated with psoriasis, a skin and nail disease.
Purines - components of certain foods that metabolize into uric acid in the body.
Rheumatic fever - a systemic disease accompanied by fever and inflammation that varies in severity, duration, and outcomes. It is frequently followed by serious heart or kidney disease.
Rheumatoid arthritis - a crippling form of arthritis characterized by painful and stiff joints on both sides of the body.
Rheumatoid factor (RF) - detects whether rheumatoid factor is present in the blood (an antibody found in the blood of most, but not all, people who have rheumatoid arthritis, as well as other rheumatic diseases).
Rheumatologist - a physician who specializes in the treatment of arthritis and other rheumatic diseases that may affect joints, muscles, bones, skin, and other tissues.
Scleroderma (also called systemic sclerosis) - chronic, degenerative connective tissue disease that affects the joints, skin, and internal organs.
Septic (infectious) arthritis - an infection in the joint fluid and tissues.
Soft tissue - the ligaments, tendons, and muscles in the musculoskeletal system.
Spondylitis - inflammation of the spine.
Spondyloarthropathy - one of a group of rheumatic diseases characterized by inflammation of the spine and sacroiliac joints, a family history of the disease, similar non-arthritic signs, and the absence of rheumatoid factor (RF) in the blood.
Synovial fluid - a clear, sticky fluid that is released by the synovial membrane and acts as a lubricant for joints and tendons.
Synovial membrane - a tissue that lines and seals the joint.
Systemic juvenile rheumatoid arthritis - a form of juvenile rheumatoid arthritis that affects joints and sometimes internal organs.
Systemic lupus erythematosus (also called SLE or lupus) - an autoimmune disorder characterized by periodic episodes of inflammation of joints, tendons, and other connective tissues and organs.
Tendons - the tough cords of tissue that connect muscles to bones.
Vasculitis - inflamed blood vessels.
X-ray - a diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.