The Facts
Arthritis is a chronic disorder that affects 1 in 5 Americans, half of whom are under 65 years of age. The word arthritis is derived from the Greek words arthron for "joint," and itis for "inflammation." Today, the term is used for over 100 different varieties of joint problems that have specific symptoms, such as pain, swelling, and stiffness.
Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common types of arthritic conditions. Other types of arthritis include gout, ankylosing spondylitis, systemic lupus erythematosus (SLE or lupus), and psoriatic arthritis.
The effects of arthritis are often mild, but in some cases they can be crippling. RA affects 1 to 2 out of every 100 people, with more women than men being affected. Joints and other organs may be affected by this form of arthritis. The Arthritis Foundation estimates that almost every person over the age of 60 years probably has OA to some degree, but fewer than half have it severe enough to notice any symptoms. OA occurs equally in both sexes but in people under 45 years of age, it is more common in men.
Causes
Some types of arthritis are genetic or inherited (i.e., they tend to run in families). Others are related to a chemical imbalance or are due to an overactive immune system. All forms of arthritis affect the joints; however, some also involve the muscles and connective tissues of the body.
Osteoarthritis (OA) is the most common form of arthritis, primarily affecting people over the age of 60 years. It is degenerative in nature - cartilage in the joints gradually wears away, causing the ends of the bones to rub against each other. OA can develop spontaneously for no apparent reason or be due to a secondary cause, where the joint damage results from an injury or trauma. Wear-and-tear is the principal cause of OA but it is now recognized that flare-ups may occur that have an inflammatory component. An athlete who has suffered joint injuries or someone who works in a job that puts daily stress on the joints is at higher risk of developing OA later in life.
Rheumatoid arthritis (RA) is caused by inflammation and thickening of the joint's lining, called the synovium. Scientists believe inflammatory forms of arthritis such as RA may be triggered by bacterial or viral infections heightened by a flaw in the body's immune system. The result is an abnormal immune response that destroys the body's own tissues - in the case of RA, the joints are the target.
Some forms of arthritis are due to metabolic problems, called crystal-associated arthritis. These include gout and pseudogout, which are caused by crystal deposits within the joints. 80% of gout sufferers are men. Gout is often genetic, but it can also be precipitated by excessive alcohol consumption, obesity, and conditions that suddenly break down large amounts of tissue. Gout results from the accumulation of uric acid, a waste product from the breakdown of digested foods. Excess uric acid forms sodium urate crystals that collect in many tissues, including the joint linings - this causes inflammation.