Osteoarthritis (OA) is a chronic condition that affects the joints. It occurs more frequently as we age. Of the more than 100 different types of arthritic conditions distinguished, OA is the most common, affecting more than 20 million people in the United States along. It is estimated that if everyone in the U.S. population who is older than age 65 underwent x-rays of their joints, more than half would show evidence of OA in at least one joint. While more than half of the population older than 65 may have OA, however, a large fraction will not. At one time OA was thought to be part of the normal aging process, but we now understand that this disease is not an inevitable part of aging. Rather, OA is believed to develop in any particular individual as a result of a combination of genetic susceptibility and environmental factors.
Osteoarthritis (OA)
A type of arthritis characterized by pain and stiffness in the joints, such as those in the hands, hips, knees, spine, or feet; it is caused by the breakdown of cartilage.
Osteoarthritis is not an inevitable part of aging. Rather, it is believed to develop in any particular individual as a result of a combination of genetic susceptibility and environmental factors.
OA is characterized by inflammation and eventual loss of the cartilage in one or more joints. Cartilage is a complex substance composed of proteins and sugars that serves as a “shock absorber” between the bones of the joints. OA commonly affects the joints of the hands, feet, and spine, as well as the large weight-bearing joints, such as those in the hips and knees.
Symptoms of OA include joint pain, tenderness, decreased range of motion in the affected joints, and a variable amount of swelling and inflammation. OA is a progressive disease, meaning that the symptoms of pain and stiffness tend to worsen over time. The amount of pain and disability that any particular patient will experience is difficult to predict, however. Some patients have OA without symptoms, where the disease is found only incidentally on x-rays. Others have disease that can progress to serious disability and the need for surgery.
The term osteoarthritis is derived from a Latin term meaning “joint inflammation.” Although the joints affected by OA may exhibit a small amount of inflammation, OA is not considered an inflammatory disease like rheumatoid arthritis (RA). Thus the term OA is technically inaccurate. Some alternative names have therefore been suggested for this condition, including osteoarthrosis, hypertrophic osteoarthritis, and degenerative joint disease (DJD).
Degenerative joint disease (DJD)
Joint destruction that occurs over a long period of time. This term is used synonymously with the term “osteoarthritis.”
Although it is often referred to as a disease, OA is more appropriately called an arthritic condition that affects one or more joints. This condition results from a variety of disorders that lead to similar symptoms and joint changes. Rheumatologists separate patients with OA into two categories—primary and secondary—based on the cause of the arthritis:
- Most patients have primary OA. Primary OA suggests that the patient has no identifiable predisposing cause for the arthritis.
- Patients with secondary OA have an underlying cause for their joint symptoms, such as congenital hip dislocation, major trauma to the joint, joint infection, or a metabolic disease such as hemochromatosis or gout.
Primary osteoarthritis
The gradual breakdown of cartilage that occurs with age and is caused by stress on a joint.
Secondary osteoarthritis
Osteoarthritis that results from trauma to the joint or from chronic joint injury due to another type of arthritis, such as rheumatoid arthritis.
Clinically, it is generally not important to make a distinction between the two forms, because their treatment is similar.