National Institute of Arthritis and Musculoskeletal and Skin Diseases
Key Words continued...
Estrogen – the major sex hormone in women.
Estrogen is known to play a role in regulation of bone growth. Research
suggests that estrogen may also have a protective effect on cartilage.
Glucosamine – a substance that occurs
naturally in the body, providing the building blocks to make and repair
cartilage. See the “glucosamine and chondroitin sulfate” section under
Complementary and Alternative Therapies for more information.
Heberden’s nodes – small, bony knobs
associated with osteoarthritis of the hand that can occur on the joints of the
fingers closest to the nail.
Hyaluronic acid – a substance that gives
healthy joint fluid its viscous (slippery) property and that may be reduced in
people with osteoarthritis. For some people with osteoarthritis of the knee,
replacing hyaluronic acid with injections of agents referred to as
viscosupplements is useful for increasing lubrication, reducing pain, and
Joint capsule – a tough membrane sac that
holds the bones and other joint parts together.
Ligaments – tough bands of connective tissue
that attach bones to each other, providing stability.
Magnetic resonance imaging (MRI) – provides
highresolution computerized images of internal body tissues. This procedure
uses a strong magnet that passes a force through the body to create these
Muscles – bundles of specialized cells that
contract and relax to produce movement when stimulated by nerves.
Nonsteroidal anti-inflammatory drugs (NSAIDs)
– a class of medications available over the counter or with a prescription that
ease pain and inflammation. Commonly used NSAIDs include ibuprofen (Advil,
Motrin), naproxen sodium (Aleve), and ketoprofen (Orudis, Oruvail). For
information about the risk posed by NSAIDs, see “NSAIDs” in the “How Is
Osteoarthritis Treated?” section.
Osteoarthritis – the most common form of
arthritis. It is characterized by the breakdown of joint cartilage, leading to
pain, stiffness, and disability.
Osteophytes – small growths of bone that can
appear on the edges of a joint affected by osteoarthritis. These growths are
also known as bone spurs.
Prolotherapy – an unregulated, unproven
therapy for chronic musculoskeletal pain. Prolotherapy uses an irritant
solution, which is injected into painful ligaments and adjacent joint spaces to
promote inflammation and subsequent healing.
Proteoglycans – components of cartilage. Made
up of proteins and sugars, strands of proteoglycans interweave with collagens
and form a mesh-like tissue. This allows cartilage to flex and absorb physical
Rheumatoid arthritis – a form of arthritis in
which the immune system attacks the tissues of the joints, leading to pain,
inflammation, and eventually joint damage and malformation. It typically begins
at a younger age than osteoarthritis does, causes swelling and redness in
joints, and may make people feel sick, tired, and uncommonly feverish.
Rheumatoid arthritis may also affect skin tissue, the lungs, the eyes, or the
Stem cells – primitive cells, usually taken
from the bone marrow, that can transform into other kinds of cells, such as
muscle or bone cells. In the future, researchers hope to be able to insert stem
cells into cartilage and stimulate them to replace cartilage damaged by
arthritis or injury.