Arthritis is a chronic disorder that affects 1 in 5 Americans, and 50% of those over 65 years of age. It is one of the major reasons people see their physicians.
The word arthritis is derived from the Greek words arthron for "joint" and itis for "inflammation." Today, the term is used for hundreds of different varieties of joint problems that have specific symptoms, such as pain, swelling, and stiffness. Arthritis means a change inside a joint. (Bursitis and tendonitis by themselves are not arthritis, because they affect tissues around the joints.)
Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common types of arthritis 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. It is also much more common in overweight people.
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 to some degree, but others may have their most serious effects on other parts of the body.
OA is the most common form of arthritis, primarily affecting people over the age of 60 years, or in younger people who have had serious joint injuries. 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. By far the greatest risk factor for OA of the hips and joints of the legs is being overweight.
"Wear-and-tear" is the principal sign of OA, but science has begun to unravel the specific mechanisms by which the disease occurs. Inflammation does not play as great a role as in other types of arthritis, but in some cases can be a prominent feature. 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.
RA is caused by inflammation and thickening of the joint's lining, called the synovium. Scientists suspect that 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, but no proof has as yet been found. The result is an abnormal immune response that destroys the body's own tissues; in the case of RA, the joints are the primary 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, but women become equally prone after menopause.
Gout may be 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 proteins. Excess uric acid forms sodium urate crystals that collect in many tissues, including the joint linings, which causes inflammation. It can also lead to kidney stones.