Knee Arthritis: Risk Factors
Written by Mitchell Robinson
Osteoarthritis (OA) is the most common joint condition in the human body. The knees are one of the most common joints for experiencing arthritis pain with more than one in eight Australian adults suffering from this condition. Knee arthritis has often been described as “wear and tear” of the cartilage of the knee joint (similar to the tyres of your car running out of tread), but we're now discovering that knee OA is much more complex than that (1).
This is partly because researchers still aren’t clear if the thinning of the articular cartilage is what causes people to experience the pain, stiffness and other symptoms associated with knee arthritis. Articular cartilage itself doesn’t have any nerve supply and there are many other structures within the knee joint which can produce pain. This is complicated by the fact that many people appear to have thinning of the articular cartilage on x-rays but don’t have any knee pain or other symptoms associated with arthritis (2). Rather than looking at knee arthritis from a cartilage “wear and tear” approach, we need to start looking at it as a whole knee problem, with multiple contributing factors including general health.
What are the risk factors?
Age
- We're all getting older! And unfortunately, ageing is a factor which can contribute to mechanical and traumatic degradation of the knee joint. But just because you're getting older doesn't doom you to having knee OA! You can reduce your chances by protecting yourself with appropriate exercise! Ageing is only one part of the process.
Gender
- Females are more likely to develop knee arthritis than males. But don't worry ladies, males are much more likely to develop hip arthritis.
Genetic factors
- If you have other family members who have had arthritis pain previously, there is a higher chance that you will too. If you fall into this category, don't be too discouraged - you can fight back with appropriate exercise!
Previous sports injuries
- If you were very physically active when you were younger - great! That doesn't increase your chances of developing knee OA. However, significant injury (e.g. ACL rupture, meniscal tear etc.) does appear to increase your chances of developing OA later in life (3).
Physical inactivity
- One of the problems with the term “wear and tear” is that it implies it’s probably better to use the joint less. This is NOT true. In fact, the opposite is true; for articular cartilage to remain healthy and regenerate, it needs a moderate amount of exercise, activity or load.
Obesity
- This is a problem for a couple of reasons. The excess load on the knee joint in itself can be problematic. However, the main problem concerns changes in hormone levels and increased inflammation associated with higher levels of adipose (fat) tissue. Obesity (especially increased abdominal fat) creates an inflammatory environment in the body which can make you more sensitive to feeling pain!
Intrinsic knee factors
- Those who report symptoms of knee OA tend to have reduced i) flexibility, ii) strength, iii) endurance and iv) control. The good news is that all of these are modifiable!
Poor mental health
- Mental health issues such as anxiety and depression, as well as having unhelpful beliefs about your body and your prognosis, can contribute to pain exacerbation (4).
Next in this series: Knee Osteoarthritis Part 2 - Signs and Symptoms
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References:
1. Berenbaum, F. (2013). Osteoarthritis as an inflammatory disease. Osteoarthritis and Cartilage, 21, 16-21.
2. Bedson, J., & Croft, P. (2008). The disconcordance between clinical and radiographic knee osteoarthritis: A systematic research and summary of the literature. BMC Musculoskeletal Disorders, 9, 116.
3. Muthuri, S., McWilliams, D., Doherty, M., & Zhang, W. (2011). History of knee injuries and knee osteoarthritis: A meta-analysis of observational studies. Osteoarthritis and Cartilage, 9, 11, 1286-1293.
4. Phyomaung, P., Dubowitz, J., Cicuttini, F., Fernando, S., Wluka, A., Raajimaakers, P., Wang, Y., & Urquhart, D. (2014). Are depression, anxiety and poor mental health risk factors for knee pain? A systematic review. BMC Musculoskeletal Disorders, 15, 10.
