Osteoarthritis -- Introduction

  • What is Osteoarthritis?
  • Who has Osteoarthritis?


    The term arthritis refers to more than 100 different diseases that affect the joints (the places in your body where bones meet) and, sometimes, muscles and other tissues. These diseases fall into two categories. One form of arthritis—called degenerative arthritis or osteoarthritis—results from the breakdown of the cushioning tissue inside joints called cartilage. The other form of arthritis—called inflammatory arthritis—results from inflammation (redness, warmth, and swelling) in the joints. Rheumatoid arthritis is a type of inflammatory arthritis.

    Osteoarthritis is the most common form of arthritis. However, most people with osteoarthritis can manage their symptoms and lead productive lives. If you have arthritis, the more you know about the disorder, the more successful your treatment is likely to be and the better control you'll have over your symptoms. The more you understand osteoarthritis, the better you can make well-informed decisions about your treatment, and use the many self-help techniques described here.

    What is osteoarthritis?

    Osteoarthritis affects a part of the joint called cartilage, a tough, rubbery tissue that covers the ends of the bones that meet at the joint. Cartilage serves as a shock absorber, or cushion, between the bones, providing a smooth surface that allows the bones to move against each other with less friction. The joint is surrounded and protected by a slippery, fluid-filled membrane called the synovial membrane. The synovial membrane and its fluid also help the joint move smoothly. A tough capsule that surrounds the synovial membrane provides additional protection for the joint.

    Osteoarthritis, which is sometimes called degenerative joint disease, occurs when the cartilage breaks down and gradually becomes rougher and thinner. Swelling can occur if the synovial membrane becomes irritated and produces excess fluid that collects inside the joint. As the cartilage wears away, growths of bone (called bone spurs) may form around the edges of the joint, making it look knobby and swollen. As the process continues, a substantial amount of cartilage wears away, causing the bones that meet at the joint to rub against each other. Because bone is very sensitive, this can be extremely painful and can severely reduce movement in the joint.

    Who has osteoarthritis?

    At least 2 to 3 percent of adults, including half of those older than 65, have osteoarthritis to some degree. As the general population ages, the disease will become even more common. Osteoarthritis in the knees and hands occurs more frequently in women; in the hips, the disease affects men and women equally.

    Osteoarthritis usually results from injury to a joint or from wear and tear on the joints over time. The following factors can increase your risk of developing osteoarthritis:

    Osteoarthritis Index