For most people, the cause of osteoarthritis is unknown, but metabolic, genetic, chemical, and mechanical factors play a role in its development. It is associated with the aging process and is the most common form of arthritis.
It may first appear without symptoms between 30 and 40 years of age and is present in
almost everyone by the age of 70. Symptoms generally appear in middle age. Before the age
of 55 it occurs equally in both sexes. However, after 55 the incidence is higher in women.
The degeneration of the joint may begin as a result of trauma to the joint, occupational overuse, obesity, or mal-alignment of the joints (for example being bow-legged or knock-kneed).
Until the late 1980s, OA was regarded as an inevitable part of aging, caused by simple
"wear and tear" on the joints. This view has been replaced by recent research
into cartilage formation. OA is now considered to be the end result of several different
factors contributing to cartilage damage, and is classified as either primary or
Primary osteoarthritis Causes
Primary OA results from abnormal stresses on weight-bearing joints or normal stresses operating on weakened joints. Primary OA most frequently affects the finger joints, the hips and knees, the cervical and lumbar spine, and the big toe. The enlargements of the finger joints that occur in OA are referred to as Heberden's and Bouchard's nodes. Some gene mutations appear to be associated with OA. Obesity also increases the pressure on the weight-bearing joints of the body. Finally, as the body ages, there is a reduction in the ability of cartilage to repair itself. In addition to these factors, some researchers have theorized that primary OA may be triggered by enzyme disturbances, bone disease, or liver dysfunction.
Secondary osteoarthritis Causes
Secondary OA results from chronic or sudden injury to a joint. It can occur in any joint. Secondary OA is associated with the following factors:
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