Osteoarthritis (OA) is the most common form of joint disease. This chronic, degenerative disorder results from the biochemical breakdown of cartilage in the synovial joints. Its symptoms tend to develop gradually and include joint aches, stiffness and swelling.
Some joints, like the ankles, may be spared due to a unique resistance of their articular cartilage to loading stress. Treatment options to reduce pain and disability can include lifestyle changes (diet, exercise), therapies, medication and surgery.
Osteoarthritis is classed as either primary or as secondary to a diagnosed cause.
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This is the most commonly diagnosed form of osteoarthritis and is considered to occur largely due to “wear and tear” over time. Because of this, it is associated with aging; in fact, age is the most potent risk factor of OA and the longer a person uses their joints, the more likely they are to suffer from this form of OA. Theoretically, this means that primary OA is inevitable should we live to an advanced enough age.
People tend to develop this type of osteoarthritis starting from the age of 55 or 60. It may be localized to certain joints; therefore, primary OA is usually subdivided by the site of involvement (eg, hands and feet, knee, hip) though it may also involve multiple joints.
This form of osteoarthritis results from conditions that induce a change in the microenvironment of the cartilage. Such conditions include significant trauma, congenital joint abnormalities, metabolic defects (eg, Wilson disease), infections, diseases (eg, neuropathic), and disorders that alter the normal structure and function of cartilage (eg, Rheumatoid Arthritis, gout).
Secondary osteoarthritis tends to appear in relatively young individuals aged approximately 45 or 50.
Common risk factors that can lead to secondary osteoarthritis include:
- Trauma: Fracturing a bone (common during sports) increases the likelihood of a person developing OA in the injured joint. Unfortunately, this also means that the person is more likely to suffer from OA at a younger age than those who have primary OA.
- Obesity: In a single leg stance, 3-6 times a person’s body weight is transmitted across the knees. Therefore, it stands to reason that an increase in body weight would result in additional force across the knees during walking. This weight bears down on the joints (particularly in the knees and hips) and causes them to wear away faster.
- Sedentary lifestyle: Not only does this promote weight gain but inactivity is also correlated with weaker muscles and tendons surrounding the joints. This increases the risk of developing OA because the muscles are not strong enough to keep the joints correctly aligned, stable and supported. It is because of this that it is so important to engage in low-impact activities that emphasize stretching, strengthening, posture, and range of motion. These include aerobics, swimming and yoga.
- Heredity: Epidemiological studies of family history have recently shed evidence of a genetic influence on OA (particularly in the hands, knees and hips). Twin studies have shown that heritability varies depending on the afflicted joint but overall, they suggest a heritability of OA of 50% or more. Studies have also suggested the involvement of specific chromosomes (e.g. 2q, 9q, 11q, and 16p) and genes such as CRTM (cartilage matrix protein), CRTL (cartilage link protein), and collagen II, IX, and XI.
- Joint overuse: This is either due to repetitive joint use in an occupation or during leisurely activity. One reason this happens during work is that over long days, the muscles will gradually become tired and no longer serve as effective joint protectors.
- Other conditions: These may include peripheral neuropathies and neuromuscular disorders that put abnormal stress on the joint. Diseases that cause inflammation, such as rheumatoid arthritis, can increase your risk of getting osteoarthritis later in life.
What is Osteoarthritis?