The number of people affected by knee osteoarthritis has more than doubled over the past 50 years, possibly due to a sedentary lifestyle and poor diet. But not only. A few basic lifestyle rules can help you protect your knees from osteoarthritis.
To better understand whether the current incidence of arthritis of the knee is really higher than in the past, a team of researchers examined the presence of this osteoarthritis on the skeletons of people aged 50 and over who died at the beginning of the industrial era (1904-1940) or during the modern industrial era (1976-2015) and whose body mass index at the time of death was documented. The presence of osteoarthritis of the knee has also been examined in older skeletons, dating from 300 to 6000 years.
These comparisons have allowed researchers to observe that knee osteoarthritis has become twice as common since the middle of the 20th century. Concretely, their results show that 16% of “modern” skeletons showed signs of osteoarthritis, compared to 6% in those dating from the beginnings of the industrial era and 8% in prehistoric specimens. The severity of osteoarthritis was also greater in modern osteoarthritic skeletons, with 42% of cases showing alterations in both knees, compared to 30% for skeletons dating from the beginnings of industrialization and 17% for those from the prehistoric era.
The term “arthritis” refers to more than 100 distinct diseases that share the common characteristic of causing pain in the musculoskeletal system, particularly the joints, ligaments, and bones. The most common form of arthritis is osteoarthritis, characterized by progressive breakdown of the articular cartilage that protects the bone. These bone alterations can be very painful and incapacitating and make it difficult to perform joint movements as simple as moving the fingers, turning the wrists or bending the knees.
The two main factors of knee osteoarthritis
The knee is the main joint affected by osteoarthritis (80% of cases). So far, two main factors have been proposed to explain this high incidence of knee osteoarthritis:
1 Since the incidence of osteoarthritis increases with age, it is possible that the increase in the life expectancy of the population is accompanied by greater wear of the joints during aging.
2 The marked increase in population body weight that has occurred in recent years may also play a role. Excess weight not only exerts a mechanical overload that prematurely wears out the knee joints, but excess fat also creates chronic inflammation that contributes to this joint deterioration.
The steep rise in knee osteoarthritis observed in recent years cannot be explained solely as an inevitable consequence of the aging population or the obesity epidemic.
Physical inactivity, another major factor in knee osteoarthritis
According to the authors, it is likely that other factors come into play, in particular our extremely sedentary lifestyle: it may seem paradoxical, but the lack of exercise is very bad for the joints! For example, in people who move little, the articular cartilages are less stressed and become thinner, which promotes the development of osteoarthritis. The muscles around the joints are also weakened and can no longer hold the knee cartilage properly.
Factors that protect the knee from osteoarthritis
Dietary habits also play an important role: the modern diet high in fat and sugar promotes the creation of a climate of chronic inflammation in the joints which can contribute to the deterioration of the cartilage of the joint. It is also interesting to note that people who develop other diseases associated with a sedentary lifestyle and this type of unbalanced diet (cardiovascular disease, type 2 diabetes) are also often affected by knee osteoarthritis, which strongly suggests the presence of similar risk factors.
We must therefore see osteoarthritis of the knee as another example of a chronic disease whose development is strongly influenced by our lifestyle. And as with all chronic diseases, the best way to prevent these joint disorders is to move more, eat more plants and reduce the consumption of pro-inflammatory foods such as processed products overloaded with sugar and fat.
Wallace IJ: Knee osteoarthritis has doubled in prevalence since the mid-20th century. proc. Natl Acad. SciUSA;114:9332-9336.