Identifying Risk Factors
There is probably no single cause of osteoarthritis, and for most people the cause is never determined, but certain risk factors have been identified.
Older age is a leading risk factor, although research indicates that joint deterioration is by no means an inevitable part of aging. Younger persons occasionally develop osteoarthritis. In particular, people who sustain significant injuries and those who are subject to small, repetitive injuries (such as work-related activities) may be at increased risk of developing osteoarthritis. For example, a jackhammer operator may be prone to developing osteoarthritis of the wrist because of repeated trauma.
A leading cause of osteoarthritis in early adulthood is a prior sports injury or fracture. In addition, evidence is accumulating to support a genetic component to osteoarthritis.
Obesity and family history are also risk factors for osteoarthritis, although neither is sufficient to cause osteoarthritis; many people who are obese or who have a strong family history never develop osteoarthritis.
Other conditions that can lead to osteoarthritis include:
- Repeated episodes of bleeding into the joint — This may occur in people with hemophilia or related bleeding disorders. Bleeding into the joint may irritate the joint, making it more susceptible to osteoarthritis.
- Repeated episodes of gout or pseudogout — These arthritic disorders may cause enough joint inflammation over time that the joint develops osteoarthritis.
- Avascular necrosis — In this condition, the blood supply to the bone near the joint is interrupted, leading to bone death and, eventually, joint damage.
- Chronic joint inflammation — This may be caused by any long-standing inflammatory joint disease, such as rheumatoid arthritis.
- Metabolic disorders — For example, hemochromatosis — one type of metabolic disorder — is a genetic disease that leads to too much iron in the joints and other parts of the body. This excessive iron changes the structure of the joints, which may lead to osteoarthritis.
- Joint infection — Bacterial or fungal infections of the joint may cause joint inflammation, leading to osteoarthritis.
When another (primary) medical condition causes osteoarthritis, health-care providers refer to the joint disease as "secondary" osteoarthritis. When osteoarthritis develops in an unusual location, such as the elbow, or at an early age, health-care providers suspect secondary osteoarthritis and search for an underlying condition. Most osteoarthritis is, however, "primary" or "idiopathic," meaning that it has no identifiable cause.
Researchers are investigating the types of changes that take place within osteoarthritic joints as they deteriorate. For example, some researchers are looking into the idea that abnormal enzymes released by cartilage cells may lead to cartilage breakdown and joint destruction. Others are investigating the possibility that some people are born with defective cartilage or slight defects in the way joints fit. As they age, these people may be more likely to experience cartilage breakdown in vulnerable joints.
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