Wear and tear has been the culprit for knee OA (osteoarthritis) for decades. This is now being challenged and is a controversial topic in the physiotherapy world. So instead of wear and tear, I’m proposing, “S.A.D. and Poor”. S.A.D. meaning the “Standard American Diet”. And Poor meaning poor movement quality and quantity. Let’s get into it. 

I get tons of patients that come into the clinic that are confused as to why their physician ordered physical therapy for their knee OA when the narrative has been that wear and tear breaks down cartilage. My job is to convince them that movement is good for them. It’s no easy task. So first off, it’s questionable at best that breakdown of cartilage even is the cause of pain. A 2020 study by Bacon et al, found that cartilage loss is correlated with only a small amount of worsening pain in the knee, and pain is also associated with synovitis of the knee (inflammation of the tissue that lines the capsule). So that is issue number 1. Then there is the movement quantity debate. In another 2020 study by Chang et al, knee pain was studied in 1194 subjects over a 10 year period. They found that long-term low-to-moderate physical activity or any strenuous activity was not associated with evidence of radiographic knee OA. This is just one study of many that keeps proving that once again, movement is good for you. 

There is a principle called “Wolff’s Law”, that states that tissues of the body will adapt to the load placed upon them. In other words, if you work out and place strain on muscles, they get stronger. Same thing with bone. Conversely, if you do nothing, they deteriorate. That’s why astronauts come back from space with severe osteoporosis; the weightless environment makes it difficult for them to put load on their joints. The research continues to point in this direction; in 2020, Maurer et al found that long term inactivity (14 years) was strongly correlated with disc degeneration of the thoracic and lumbar spine. So why are we telling patients to stop loading their knees when they have degeneration. It seems counterintuitive. 

So what is the culprit? Instead of “wear and tear”, I put forth “S.A.D. and Poor”. The Standard American Diet, we all know, is pretty pathetic. Processed foods, simple sugars, vegetable oils, all combined with a busy lifestyle and fast food joints on every corner. This is the equation for the perfect storm of chronic inflammation. In 2017, Bricca et al state that proinflammatory factors lead to the breakdown of the articular cartilage in the extracellular matrix. So perhaps, poor food choices lead to chronic inflammation and widespread degeneration. 

Poor movement quality and poor movement quantity are also deleterious to the knee. What do I mean? Well we’ve already addressed quantity. It appears not moving enough can lead to degeneration. Of course, how we move matters too; and this is what I mean by quality. If your knee caves in with every step you take because of imbalances and weaknesses, this will certainly cause some issues. I see it this way; there is an ideal way to squat, step, stride, etc. The more your movement pattern deviates from ideal, the more at risk for injury you are. 

So what’s the bottom line? Eat well, and move. Are you surprised? 

References: 

Bacon, K.l., et al. “Does Cartilage Loss Cause Pain in Osteoarthritis?” Osteoarthritis and Cartilage, vol. 28, 2020, doi:10.1016/j.joca.2020.02.230.

Chang, Alison H., et al. “Association of Long-Term Strenuous Physical Activity and Extensive Sitting With Incident Radiographic Knee Osteoarthritis.” JAMA Network Open, vol. 3, no. 5, Apr. 2020, doi:10.1001/jamanetworkopen.2020.4049.

Maurer, Elke, et al. “Long-Term Effect of Physical Inactivity on Thoracic and Lumbar Disc Degeneration – a MRI Based Analysis of 385 Individuals from the General Population.” The Spine Journal, 2020, doi:10.1016/j.spinee.2020.04.016.

Bricca, A., Juhl, C., Grodzinsky, A., & Roos, E. (2017). Impact of a daily exercise dose on knee joint cartilage – a systematic review and meta-analysis of randomized controlled trials in healthy animals. Osteoarthritis and Cartilage,25(8), 1223-1237. doi:10.1016/j.joca.2017.03.009