Very few people, as well as very few doctors, understand the etiology or the natural history of osteoarthritis (OA) well. For the most part, osteoarthritis is a biological disease, as opposed to the belief that osteoarthritis is a mechanical disease.
Far too many still believe that physical activity causes OA, or cartilage loss due to wear and tear.
Simply put, OA is the loss of cartilage in the knee. Lose a little cartilage, and you have mild OA; lose a lot, and you have a more severe case.
For the most part, you can ignore your X-ray findings. Treatment decisions should be based on your symptoms. Not your X-ray appearance.
Words harm. Let's say you're a runner, and your knees ache after a long run. Perhaps they swell a little, too. You go to see a specialist, and they typically explain your X-rays in one of three ways:
- "Your X-rays show bone-on-bone arthritis."
- "You have the knee of an 80-year-old."
- "You have some arthritis in your knee."
After which of those descriptions are you going to head out tomorrow to run?
How we describe imaging findings can have a dramatic impact on you. Far too many people do not receive an accurate education of what a life with OA means. I mentioned earlier that OA is not usually caused by trauma or wear and tear.
Cartilage, or the firm, shiny substance on the ends of your bones, is a living tissue. But it doesn't receive blood flow. Without blood flow, it isn't directly exposed to nutrients found within our blood vessels. Our cartilage is nourished by joint fluid. Cartilage needs cyclical loading for nourishment. The loading helps push the joint fluid into the cartilage cells.
Runners are often told that running will ruin their knees. That is plainly false, as many studies have shown. Cartilage likes the cyclical loading associated with running. Like our brain, heart, and muscles, cartilage doesn't like being sedentary.
Our metabolic health affects our cartilage, too.
This concept is important. This is the number one reason why the incidence of osteoarthritis is increasing rapidly. Cartilage receives its nutrition from joint fluid. The nutrients diffuse into our joint fluid from the blood supply to our joints. That can be good... or bad.
Osteoarthritis is due to the loss of cartilage health. This is one of the initiating events. A cascade of changes takes place downstream that includes changes to the thickness of the cartilage, bone inflammation, new nerve growth (pain), changes to the cells in the knee (more inflammatory), and structural changes (bone spurs).
Many things can affect cartilage health. Prior injuries or trauma can injure the cartilage. So can previous surgery. However, the cause of osteoarthritis that is scaling most rapidly is "metabolic disease-associated OA," or MDOA. Wait, what?
In the balance of this piece, for paid members only, I go deeper into the science, the myths, and the metabolic factors.