IS PHYSICAL ACTIVITY A RISK FACTOR FOR DEVELOPING OSTEOARTHRITIS?
Traditionally, osteoarthritis has been classified as two types. Primary osteoarthritis, associated with ageing and genetic factors and secondary osteoarthritis which is caused by others factors such as obesity, joint injury, repeated joint use, high blood pressure, hypercholesterolaemia, hyperglycaemia, etc.
Although exercising implies repetitive movements of the joints that could cause joint wear due to overuse, it has been shown that physical activity is beneficial in preventing osteoarthritis.
In the first place, exercising reinforces the muscles surrounding the joints and therefore reduces the risk of suffering joint injury.
Secondly because physical activity prevents deterioration of the joints through lack of use and improves y maintains joint mobility.
Thirdly, because it helps prevent obesity, a very important risk factor for the development of osteoarthritis.
The relationship between obesity and osteoarthritis goes beyond mere joint wear caused by the excess weight they have to support, as the prevalence of osteoarthritis in the hands is also higher among obese people. Overweight and obesity cause and aggravate osteoarthritis, irrespective of the joint overload due to excess weight, through a metabolic pathway. It is well known that fatty tissue acts as an endocrine gland, releasing inflammatory substances directly involved in cartilage degradation.
And finally, physical activity in itself promotes the natural joint balance process.
The cartilage layer covers the joint surface and its function is to cushion and reduce the friction whenever there is movement, preventing one bone from rubbing against another. As cartilage has no blood vessels or nerve endings, cartilage cells (chondrocytes) get their nourishment through substances released by the synovial fluid surrounding the joint.
The synovial fluid is a viscous and elastic substance, rich in hyaluronic acid whose main function is precisely that of nourishing cartilage. Synovial fluid also has mechanical actions: it lubricates the joint, protecting it from knocks.
When we move our joints we encourage the synovial fluid to penetrate joint cartilage and therefore we are fostering cartilage and joint nutrition and performance.
However, it has also been shown that the risk of suffering osteoarthritis is higher among professional athletes and people with certain types of professions that involve repetitive physical activity.
In reality, there is no consensus about whether physical activity increases the risk of osteoarthritis or not. It depends on the type of activity and the intensity.
According to a trial carried out in the United States with 17,000 people between 20 and 87 years of age there is a correlation between physical activity and osteoarthritis. The study, published in the Journal of Clinical Epidemiology, concludes that high intensity physical activity such as running more than 30 km a week doubles the probability of osteoarthritis in men under 50 years of age; although this relationship was not confirmed in women (of any age) or in men over 50.
Other studies however, suggest that long-term training is not necessarily associated with an increased probability of osteoarthritis.
A study published by the Medicine & Science in Sports and Exercise journal and carried out in the United States with 75,000 runners and 15,000 walkers, concluded that runners (including those running more than 30 km a week) have less risk of developing osteoarthritis or of requiring hip replacement. The authors of the study claim that this could be explained in part by the fact that runners have a lower body mass index and it is already known that overweight and obesity are risk factors for developing osteoarthritis. The study also demonstrated that other sports are correlated with a higher probability of suffering osteoarthritis or requiring knee replacement surgery.