Osteoarthritis, also known as a degenerative joint disease (DJD), is the most common type of arthritis. Osteoarthritis is more likely to develop as people age. The changes in osteoarthritis usually occur slowly over many years, though there are occasional exceptions. Inflammation and injury to the joint cause bony changes, deterioration of tendons and ligaments, and a breakdown of cartilage resulting in pain, swelling, and deformity of the joint.
There are two main types of osteoarthritis:
- Primary: Most common, generalized, primarily affects the fingers, thumbs, spine, hips, knees, and the great (big) toes.
- Secondary: Occurs with a pre-existing joint abnormality, including injury or trauma, such as repetitive or sports-related; inflammatory arthritis, such as rheumatoid, psoriatic, or gout; infectious arthritis; genetic joint disorders, such as Ehlers-Danlos (also known as hypermobility or “double-jointed; congenital joint disorders; or metabolic joint disorders.
Who is affected by osteoarthritis?
Approximately 80% of older adults, ages 55 years and older, have evidence of osteoarthritis on X-ray. Of these, an estimated 60% experience symptoms. It is estimated that 240 million adults worldwide have symptomatic osteoarthritis, Post-menopausal women have an increased incidence of knee osteoarthritis compared to men.
What are the risk factors for osteoarthritis?
In addition to age and secondary causes such as inflammatory arthritis and prior injury/ trauma, several other risk factors increase the chance of developing osteoarthritis including obesity, diabetes, elevated cholesterol, sex, and genetics.
- Obesity is a risk factor for osteoarthritis, particularly of the knee. In addition to overloading the weight-bearing mechanisms of the body, the metabolic and pro-inflammatory effects of obesity have been studied as contributory to osteoarthritis. Maintaining ideal body weight or losing extra weight is important for those at risk.
- Both diabetes and hyperlipidemia (elevated lipids/cholesterol) contribute to the inflammatory response within the body, increasing the risk of osteoarthritis. Oxidation of lipids can also create deposits in cartilage which affects affecting blood flow of subchondral bone in the same way that blood vessels are affected by atherosclerosis. Elevated blood sugars, as well as elevated cholesterol/lipids, increase free radicals within the body, this oxidative stress exceeds the resilience of cartilage on the cellular level. Managing diabetes and hyperlipidemia is important for bone health in addition to general health.
- Decreased estrogen as experienced by post-menopausal women increases the risk of knee osteoarthritis as estrogen is protective of bone health specifically reducing oxidative stress to the cartilage.
- Heredity can play a role in osteoarthritis, as individuals born with other bone diseases or genetic traits may be more likely to develop osteoarthritis. For example, Ehlers-Danlos, which is characterized by joint laxity or hypermobility, can contribute to osteoarthritis.