What causes osteoarthritis?
Primary generalized
osteoarthritis affects women more than men, often occurring shortly after
menopause. Most people with primary osteoarthritis have other family members who
are affected by the same problem,
and usually have swelling and or pain of the finger joints, base of thumbs, and
knees or hips. Secondary osteoarthritis may occur in a joint that was previously
injured from trauma, or after the joint has been damaged by some other cause
such as infection or rheumatoid arthritis.
Although the exact mechanisms of cartilage loss and bone changes are unknown,
great advancements have been made in recent years. It is likely that complex
signaling processes during joint inflammation--and defective repair mechanisms
in response to injury--gradually erode cartilage within the joints. Other
changes cause the joint to lose mobility and function, resulting in joint pain
with activity.
Who is affected by osteoarthritis?
Although most older individuals (over 60 years old) have evidence of
osteoarthritis by x-ray, most have no symptoms. More than 20 million U.S. adults have symptomatic osteoarthritis. Women are three
times more likely than men to develop primary generalized osteoarthritis.
Because age is a risk factor, people are more likely to develop this form of
arthritis as they get older.
Are there other risk factors for osteoarthritis?
In addition to hereditary factors (genes) and other forms of arthritis, several
other risk factors increase the risk for developing osteoarthritis, including
other hereditary disorders, obesity, and injuries to or around the joint.
- Heredity plays a role in osteoarthritis as individuals
born with other diseases are more likely to develop osteoarthritis. Examples
include conditions associated with increased joint laxity (being
"double-jointed"), some dysplasias (abnormal growths of bone and
cartilage) and Paget’s disease (a type of inflammation in bone that occurs in
older people).
- Obesity is a risk factor for osteoarthritis of the lower
extremity and spine. Being overweight also may accelerate the rate of
development of osteoarthritis. Maintaining ideal body weight or losing extra weight is important for those at risk.
- Injuries (such as those occurring in many athletes)
contribute to the development of osteoarthritis. An injury that results in
abnormal stress on a joint is another important risk factor for osteoarthritis.
Overuse injuries are more controversial as many people who have similar
lifestyles do not develop osteoarthritis. However repetitive trauma – which
may result from overuse – does increase that risk.
- Other conditions that may lead to the development of
osteoarthritis include peripheral neuropathies (diseases of the nervous system) and neuromuscular disorders that
put abnormal stress on the joint.