There is no single underlying cause of osteoarthritis, which is the leading cause of joint degeneration and pain. There are several known risk factors that increase the likelihood of developing the disease. The more risk factors a person has, the more likely it is that they will develop osteoarthritis.
Osteoarthritis Risk Factors
While many risk factors cannot be changed, others, such as weak muscle tone, can be improved. Understanding the risk factors and making changes where possible may decrease the likelihood of developing or worsening osteoarthritis.
Factors known to increase susceptibility to osteoarthritis include:
The single most common cause of osteoarthritis is aging. Cartilage is likely to breakdown after decades of wear and tear. More recently, researchers have associated aging with low-grade inflammation and speculate that it may cause or exacerbate osteoarthritis.1,2
Some genes may not contribute to osteoarthritis until they are “turned on” by a particular event or stimulus. For example, older age is associated with increased levels of inflammatory proteins in the body, and these proteins may turn on certain genes that accelerate the arthritic process. The study of the interaction between genes and environmental triggers is called epigenetics.
Genes also play a role in physical abnormalities that can increase the risk of osteoarthritis. For example, hip dysplasia—a condition in which the hip’s socket is abnormally shallow—can cause extra mechanical stress on the joint that leads to osteoarthritis.
Research has clearly shown that carrying excess weight increases the risk of osteoarthritis. This is true for two reasons:
- Weight-bearing joints experience more wear and tear. For example, during walking, the knees experience a compressive load that is about 3-4 times bodyweight.9,10 Over time, an excess load can take a toll on joints.
- Obesity is associated with low-grade, systemic (body-wide) inflammation, which may contribute to the development of osteoarthritis.11-13 (Obesity is defined as a BMI ≥ 30.)
Past injury and surgeries
Old injuries and past surgeries can lead to osteoarthritis years or even decades later. For example:
- Minor damage to cartilage due to an injury or surgery may go unnoticed but worsen over time.
- An injury can change the body’s biomechanics (such as favoring one leg) and puts excess strain on certain joints, making them more prone to arthritis.
Experts estimate that 12% of cases of osteoarthritis in the hip, knee, and ankle are due to traumatic injuries.16
Joint stress and overuse
Occupations or sports that require repetitive motions over months or years can put increased stress on specific joints and increase one’s risk of developing osteoarthritis.
Sedentary lifestyle and weak muscle tone
Just as too much stress on a joint can cause arthritis, so can too little stress. For example, the knees must experience some weight-bearing stress to encourage cartilage tissue health.17
In addition, a lack of exercise or a sedentary lifestyle can lead to muscle weakness. Weak muscles are unable to support a joint, resulting in more stress on the joint tissues, including cartilage and underlying bone. This stress can lead to osteoarthritis.
In addition to the risk factors listed above, research has identified certain biochemical changes that occur in joints affected by osteoarthritis.18 It is not clear if these changes are a cause or effect of the osteoarthritis process.
The more risk factors a person has, the more likely they are to develop osteoarthritis. While risk factors can increase the chances of developing osteoarthritis, they are not absolute. It is possible to have several risk factors and never develop osteoarthritis.