Inflammation of joints that results in pain, heat, swelling, and loss of function. Arthritis is not one condition but has many causes, and it affects more than 40 million people in the United States. Arthritis in its many forms causes considerable suffering to the affected individual and is costly for both the individual and society.

Direct medical costs for patients with RHEUMATOID ARTHRITIS averaged $8,500 per year in the late 1990s. Half of this was in hospital costs, 26 percent in medication costs, and 8 percent for physician visits. Not only do people with arthritis have these direct costs, but they may also suffer loss of earnings or require modification of their home or workplace. These are known as indirect costs and average out at roughly two and a half times the direct costs.

Approximately 5 percent of people of working age in the United States have some form of arthritis. About 25 percent of workers with rheumatoid arthritis take early retirement because of their disease, as do 14 percent of those with osteoarthritis. This contrasts with 3 percent of those without arthritis taking early retirement because of ill health.

Although it is difficult to measure scientifically, several studies now show that effective treatment reduces these costs as well as improves the quality of life. Treatment of different types of arthritis varies, and classification aids the selection of rational therapy. Arthritis-related conditions can be classified into the following categories:

1. Degenerative arthritis (osteoarthritis, OA)
2. Arthritis caused by crystal deposition
3. Rheumatoid arthritis (RA)
4. Seronegative arthritis
5. Connective tissue disorders
6. Infective arthritis
7. Arthritis caused by metabolic and systemic diseases

A diagnosis of a particular type of arthritis is usually made mainly on the symptoms and physical findings. Laboratory tests and X rays are sometimes helpful but are seldom absolutely diagnostic. Examination of synovial fluid is important in the diagnosis of arthritis caused by infections and crystal deposition, for example gout.

For a few rheumatic problems, for example VASCULITIS, a biopsy of tissue, often skin or a superficial nerve, can be diagnostic. The following clinical features of arthritis aid the diagnosis.

1. Whether it is inflammatory or noninflammatory
2. Whether its onset is acute or chronic
3. The number of joints involved and their distribution
4. The characteristics of the individual that predispose him or her to arthritis
5. The involvement of organs other than the joints

Inflammatory arthritis (RA, seronegative arthritis, crystal-induced arthritis, infective arthritis) causes pain, often worse in the morning, swelling, warmth, redness, pain on movement, and several hours of stiffness after arising.

Noninflammatory arthritis (degenerative arthritis) causes pain, often worse at night, and stiffness usually lasting only a few minutes after a joint has been in one position for a while. Soft tissue swelling, warmth, and redness are usually absent.

Acute onset of severe symptoms occurring overnight is typical of crystal-induced and infective arthritis. Most other types of arthritis have a more gradual onset, and degenerative arthritis typically becomes slowly more noticeable over years.

Arthritis can affect many joints (polyarticular), a few joints (pauciarticular or oligoarticular), or one joint (monarticular). The distribution of affected joints can be symmetrical, typically involving the same joints on both sides of the body, or asymmetrical, affecting scattered joints.

Different types of arthritis are more likely to affect people with certain characteristics at particular stages of their life. For example, gout most commonly affects middle-aged men who are overweight and drink alcohol and elderly women who are on treatment for high blood pressure or heart failure.

Connective tissue diseases like Systemic lupus erythematosus (SLE) largely affect young women, and rheumatoid arthritis usually starts between the ages of 40 and 60 years. Connective tissue diseases typically affect organs other than the joints, especially the skin, blood, nervous system, kidneys, heart, lungs, and muscle.

The organs involved may give clues to which type of arthritis it is. For example, the skin changes in a patient with scleroderma point to that diagnosis. Other diseases such as acromegaly will usually be diagnosed because of the other organs involved before the arthritis becomes a problem.

The aims of treatment are:

1. Relief of pain and suffering
2. Maintenance and restoration of function
3. Prevention of disease progression

The treatment of the various types of arthritis depends on the diagnosis, the severity of disease, the individual patient’s response to different therapies, and a person’s needs. Treatment may involve a combination of physical therapy and exercises, lifestyle alterations, medications, and surgery.

The treatment of specific types of arthritis is described under their individual entries but is summarized in the table on the next page. The prognosis of arthritis differs according to the diagnosis, severity of disease, and treatment and is discussed under individual entries.

People with certain forms of arthritis also develop related health problems such as lung, heart, and kidney disease more frequently than average. Paying careful attention to these will also improve the patient’s quality of life.