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Guide To Osteoarthritis

Part 1 of 5 - What Is Osteoarthritis?

By Carol & Richard Eustice, About.com

Updated: April 3, 2007

About.com Health's Disease and Condition content is reviewed by Kate Grossman, MD

Osteoarthritis is the most common type of arthritis, especially among older people.

Osteoarthritis is also called degenerative joint disease or osteoarthrosis.

Osteoarthritis is a joint disease that mostly affects the cartilage. Cartilage is the slippery tissue that covers the ends of bones in a joint. Healthy cartilage allows bones to glide over one another. It also absorbs energy from the shock of physical movement.

In osteoarthritis, the surface layer of cartilage breaks down and wears away. This allows bones under the cartilage to rub together, causing:

  • pain
  • swelling
  • loss of motion of the joint

Over time, the joint may lose its normal shape. Also, bone spurs (small growths called osteophytes) may grow on the edges of the joint. Bits of bone or cartilage can break off and float inside the joint space. This causes more pain and damage.

People with osteoarthritis usually have joint pain and limited movement.

Unlike some other types of arthritis, osteoarthritis predominantly affects the joints and not internal organs. For example, rheumatoid arthritis (the second most common type of arthritis) affects other parts of the body besides the joints. It begins at a younger age than osteoarthritis, causes swelling and redness in joints, and may make people feel sick, tired, and (uncommonly) feverish.

  • Is it Rheumatoid Arthritis or Osteoarthritis?
  • Osteoarthritis - Test Your Knowledge
  • Who Has Osteoarthritis?

    Osteoarthritis is one of the most frequent causes of physical disability among adults.

  • More than 20 million people in the United States have the disease.
  • By 2030, 20% of Americans (about 70 million people) will have passed their 65th birthday and will be at risk for osteoarthritis.
  • Some younger people get osteoarthritis from joint injuries, but osteoarthritis most often occurs in older people.
  • More than half of the population age 65 or older would show x-ray evidence of osteoarthritis in at least one joint.
  • Both men and women have the disease.
  • Before age 45, more men than women have osteoarthritis, whereas after age 45, it is more common in women.
  • Osteoarthritis Screening Quiz
  • How Does Osteoarthritis Affect People?

    Osteoarthritis affects each person differently. In some people, it progresses quickly; in others, the symptoms are more serious. Scientists do not know yet what causes the disease, but they suspect a combination of factors, including:

    • being overweight
    • the aging process
    • joint injury i.e. sports injuries
    • other stresses on the joints

    What Areas Are Affected?

    Osteoarthritis most often occurs at the:

  • Where Does it Hurt?
  • Osteoarthritis hurts people in more than their joints: their finances and lifestyles also are affected.

    Financial effects include:

    Lifestyle effects include:

    Despite these challenges, most people with osteoarthritis can lead active and productive lives. They succeed by using osteoarthritis treatment strategies, such as the following:

    Understanding The Joints

    Most joints (the place where two moving bones come together) are designed to allow smooth movement between the bones and to absorb shock from movements like walking or repetitive movements. The joint is made up of:

    • Cartilage: a hard but slippery coating on the end of each bone. Cartilage, which breaks down and wears away in osteoarthritis, is described in more detail below.
    • Joint capsule: a tough membrane sac that holds all the bones and other joint parts together.
    • Synovium: a thin membrane inside the joint capsule.
    • Synovial fluid: a fluid that lubricates the joint and keeps the cartilage smooth and healthy.
    • Ligaments, tendons, and muscles: tissues that keep the bones stable and allow the joint to bend and move.
      • Ligaments are tough, cord-like tissues that connect one bone to another.
      • Tendons are tough, fibrous cords that connect muscles to bones.
      • Muscles are bundles of specialized cells that contract to produce movement when stimulated by nerves.

    Cartilage: The Key to Healthy Joints

    Cartilage is 65 to 80% water. Three other components make up the rest of cartilage tissue: collagen, proteoglycans, and chondrocytes.

  • Collagen: a fibrous protein. Collagen is also the building block of skin, tendon, bone, and other connective tissues.
  • Proteoglycans: a combination of proteins and sugars. Strands of proteoglycans and collagen weave together and form a mesh-like tissue. This allows cartilage to flex and absorb physical shock.
  • Chondrocytes: cells that are found all through the cartilage. They mainly help cartilage stay healthy and grow. Sometimes, however, they release substances called enzymes that destroy collagen and other proteins.

    Go On To Part 2 --- Guide To Osteoarthritis --->

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    6. Guide To Osteo-arthritis - Your Guide To Degenerative Joint Disease (Osteoarthritis)

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