Osteoarthritis pain is caused by a wearing down of the cartilage that serves as a protective shock absorber between the joints. Cartilage is important for minimizing the impact of everyday activities on the joints, but the intensive use also means that it is subject to high levels of wear and tear.
There is no single known cause of osteoarthritis, but several risk factors can serve as strong indicators for the disease when present. Patients are at greater risk of developing osteoarthritis if they have one or more of the following factors.
- Age. The single most common cause of osteoarthritis is aging, as use of the joint over many years is likely to lead to breakdown of cartilage. Osteoarthritis develops most often in people over age 50.
- Family history. Genetics can play a role in bone abnormalities that result in distorted shape and problems with joint alignment. This is apparent in cases of bowed legs or double-jointed abilities, both of which are more likely to lead to development of osteoarthritis.
- Obesity or excess weight. Weight-bearing joints are at risk for osteoarthritis in people who are significantly overweight. It is estimated that every extra pound of weight adds three pounds of pressure on the knees, and increases the pressure on the hips as much as six times. Because weight gain gradually increases stress on the joints, the onset of osteoarthritis symptoms may take many years to develop.
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- Injury or overuse of the joint. Occupations or sports that require repetitive motion over a long period of time increase one’s risk of developing osteoarthritis due to increased stress on specific joints. Old injuries can develop into osteoarthritis, especially where a fracture or surgery has occurred. Overcompensation for injuries can also cause osteoarthritis to develop due to a modified gait or other activities.
Having a risk factor for osteoarthritis does not guarantee that the condition will develop. But the presence of a combination of risk factors produces the highest likelihood that a given person will develop the disease.