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Recently, I was meeting with a client via online video. We worked together in 2018 to help her overcome knee pain related to osteoarthritis. She was now consulting me about a different concern, but she made sure to tell me her knees were still doing great. And then she said:
“I tell everyone that I rebuilt my knee cartilage. But they tell me that’s not possible… Well, I don’t know what to tell them, but something happened: I can walk now, and I don’t have knee pain.”
When an X-ray or MRI reveals cartilage degeneration (in the cases of osteoarthritis or chondromalacia), most people want to know what they can do to change this. They essentially want to build up their cartilage so it looks as healthy as it did years ago-- back when their knees were pain free. They are looking for some type of assurance that they can get better.
And so I’m frequently asked: How long will it take my X-ray or MRI to look normal?
It’s a question that’s difficult to answer for two reasons.
(1) There are some scientific studies -- like this one -- that have demonstrated improvement on MRIs taken two years apart. However, most people are not enrolled as subjects for this type of research. Once people in the general population recover from knee pain, they rarely have another image taken.
When my clients’ knee pain resolves, they get back to living and rarely do they get another X-ray or MRI to compare what their knees looked like before and after working together. After all, if they’re walking or running, hiking or cycling, squatting, kneeling, and whatever else they enjoy doing, they don’t spend much time considering what their imaging reports look like. Because they feel great!
(2) The second reason is best explained by considering what someone does when they are sick. They use a thermometer to measure their temperature. If their temperature is above a certain level, they have a fever. When their temperature drops below that level, the fever has resolved, and they feel better. Likewise, when someone with knee pain gets an X-ray or MRI, these images may reveal a loss of cartilage (i.e., the cartilage is not as thick as it once was). But unlike having a fever-- where the reading on the thermometer must change to indicate the return to wellness-- knee pain can resolve without the X-rays or MRI improving.
This naturally leads someone to ask: If the image of the cartilage looks the same, why is there no longer knee pain?
X-rays and MRIs take a static picture of the inside of the knee. They reveal the thickness of cartilage, but they don’t reveal the strength of that cartilage.
Strong cartilage is firm. It consists of microscopic cartilage cells and water molecules that hold very tightly to one another. Strong cartilage protects the underlying bone and provides a smooth surface for motion to occur.
Weaker cartilage, on the other hand, is softer. Cartilage cells and water molecules are not bonded together as tightly. This means that the soft cartilage can not withstand activities that put pressure on the knees (such as hiking or squatting). Certain activities or certain amounts of these activities will wear off tiny bits of cartilage. This eventually causes knee pain.
Strong, protective knee cartilage is necessary to be active and free of pain. This is possible even if some of the cartilage within the knees has worn off. (I've written about this previously here.)
Multiple research studies have demonstrated the positive effects of movement and exercise on the strength and resilience of cartilage.
Two researchers, Roos and Dahlberg, published an article in 2004 stating that, “cartilage adapts to loading as other biological tissues like bone and muscle, and moderate loading seems to be beneficial both for prevention and treatment of osteoarthritis.”
The same two researchers conducted a four‐month, randomized, controlled trial of patients at risk of knee osteoarthritis. The participants were between the ages of 35 and 50 years old, and they had undergone knee surgery (specifically a partial medial meniscus resection) 3 - 5 years previously. A specialized type of MRI known as a delayed gadolinium-enhanced magnetic resonance imaging of cartilage (i.e., dGEMRIC) was used to assess the quality of the cartilage within the participants’ knees before and after the study.
The participants were randomly assigned to a group that performed supervised exercises for one hour three times per week (i.e., the exercise group), or to a group that did not receive any exercise recommendations (i.e., the control group). The researchers found an increase in the quality of cartilage within the knees of those in the exercise group.
And they concluded that, “human cartilage responds to physiologic loading in a way similar to that exhibited by muscle and bone, and that previously established positive symptomatic effects of exercise in patients with OA may occur in parallel to or even be caused by improved cartilage properties.” These findings are published in Arthritis and Rheumatism, in an article entitled “Positive effects of moderate exercise on glycosaminoglycan content in knee cartilage”.
And in 2012, Gahunia & Pritzker wrote “Effect of Exercise on Articular Cartilage,” and it was published in the journal Orthopedic Clinics of North America. In it, the authors state, “The biosynthetic activity of chondrocytes has also been experimentally shown to be regulated by mechanical stimuli.” In other words, cartilage changes based on the pressure and movement it receives. Moreover, Gahunia & Pritzker point out that, “Both clinical and animal research have shown that continuous passive motion of the joint, after joint procedures, is an important stimulus for articular cartilage regeneration.”
Continuous passive movement (CPM) machines are often prescribed following knee surgery. However, the benefits of gentle knee motion can also be achieved without this device. I frequently recommend my clients sit and place their foot on something that allows them to easily slide their foot on the floor to create a relatively passive knee movement. (To view a demonstration of this exercise, watch this.) And in other cases, I recommend an exercise machine that varies how much force occurs inside the knees.
While there is not clarity in the scientific literature about the extent to which cartilage can be rebuilt, these research findings all support the capacity of cartilage to improve given the right type and amount of exercise.
For more information regarding the approach my clients use to strengthen their cartilage, read this.
To learn more about healing knee cartilage, read my colleague's article.
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