Osteoarthritis is commonly believed, by doctors and the general population, to be a disease of aging and obesity. Knee osteoarthritis (OA) can be found in about 1/3 of all adults over 60 years old in the United States. The prevalence of osteoarthritis has doubled in just the last 50 years.
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This is how most doctors have thought about OA up until today:
- Osteoarthritis is caused by wear and tear.
- Activity causes wear and tear. The more you use your knees the faster they will wear down.
- Obesity increases wear and tear on the joints.
- The longer someone lives the more wear and tear their joints will endure.
- People are more obese today than 50 years ago which helps explain the increase in osteoarthritis.
- Osteoarthritis is more common today than 50 years ago because people are living longer.
There have been studies however that are starting to disprove this theory. A new study published in the Proceedings of the National Academy of Sciences throws the theories of aging and obesity causing knee OA out the window.
Dr. Ian Wallace from the Department of Human Evolutionary Biology at Harvard University and his 7 co-authors studied over 2000 skeletons from prehistoric, early industrial, and postindustrial United States and looked at the prevalence of knee OA. The study showed that the prevalence of knee OA has doubled in the last 50 years. To test whether age and obesity were responsible for the increase in OA, he looked at the more than 1800 skeletons for which age and BMI data were known. Postindustrial individuals were 6 years older and had 41% higher BMIs than the early industrial group. Only 1% of early industrial individuals were obese and 6% overweight compared to 25% of postindustrial individuals who were obese and 24% who were overweight. When controlling for age and BMI, the postindustrial group were 2.1 times as likely to have knee OA.
The study says:
Age and BMI were positively associated with knee OA prevalence (P<0.0001 for both variables), but at all ages, knee OA prevalence was at least twice as high in the postindustrial sample than in the early industrial sample, even after controlling for BMI.
The authors point to several factors that need further investigation and discussion and state that OA may be preventable - something Egoscue and Posture Alignment Therapists like myself have been saying for decades.
The results of this study are thus clinically significant because they indicate that knee OA may be more preventable than is currently supposed. Given evidence that nearly all knee OA is associated with loading-induced damage to joint tissues, either because the loads are abnormal or the tissues are structurally weak, one especially important source of environmental change that warrants greater attention is whether and how joint loading has altered.
As a Posture Alignment Specialist, looking at joint loading is what I do all day long. I've talked about knee joint loading previously, and will restate that knee joint loading is altered with any change in load joint alignment (ankle, knee, hip, shoulder) which comes from joint and muscle dysfunction.
 Varus knee alignment, which is caused by muscle imbalances, will cause excessive load on the inside of the knee joint. |  Valgus knee alignment causes increased forces and wear and tear on the outside of the knee joint. |
Trauma has presumably always predisposed some individuals to knee OA, as suggested by the predominate of unilateral knee OA since prehistoric times...
It is great the authors talked about how unilateral knee OA has to be explained by something other than age or obesity because those factors don't pick sides. Previous injury to the knee has been shown in previous studies to increase the chance of developing OA later in life. The other major factor that is rarely if ever discussed is posture imbalances left to right. I have seen hundreds of clients with no previous injuries that present with unilateral knee OA and they always show large left to right posture imbalances. When these imbalances are decreased, the clients experience a deduction in pain and improved ability to perform activities of daily living and exercise.
 An elevated hip will cause the body to load one hip and knee more than the other. |  Hip muscle imbalance and dysfunction is causing uneven and unnatural loading of the knees. |
...another possibility that merits more study is physical inactivity, which has become epidemic during the postindustrial era. Less physically active individuals who load their joints less develop thinner cartilage with lower proteoglycan content as well as weaker muscles responsible for protecting joints by stabilizing them and limiting joint reaction forces.
The authors make a couple very important points in the above statement. The less active we are the weaker our muscles get and the thinner our cartilage gets. The more active we are the stronger our muscles get and the thicker our cartilage gets.
Keys to preventing knee joint osteoarthritis:
- Correct any posture imbalances you have so that your load joints line up vertically and horizontally from the sagittal and frontal planes.
- Restore full joint range of motion to all your joints and use that range of motion on a daily basis.
- Load your joints with impact daily to strengthen bones and thicken cartilage.
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This shows ideal postural alignment where the ankles, knees, hips, and shoulders align vertically and horizontally, the pelvis is neutral, the spine has it's s-curve, and the feet and knees point straight ahead.
Patch Fitness is a fun and fast way to take all your joints through a full range of motion.
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Running and jumping are the two best activities to load your knees and strengthen your muscles, bones, and cartilage.
Sources:
Knee osteoarthritis has doubled in prevalence since the mid-20th century
Skeletons say arthritis isn't about aging - it's about activity
Sources:
Knee osteoarthritis has doubled in prevalence since the mid-20th century
Skeletons say arthritis isn't about aging - it's about activity
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