Some Good News About Cartilage's Ability to Rebuild Itself

I’ve said before that there won’t be a third edition of Saving My Knees because I expect that what lies between the covers will eventually no longer seem that radical and will become widely accepted.

And, happily, along comes a New York Times article to underscore that very point.

To recap, what I’ve said (in the book and on this blog):

The cartilage in your knees doesn’t simply “wear out.” It’s not like the tires on your car. It has an underappreciated ability to adapt and even repair itself (though very slowly).

To be clear, these insights don’t originate with me.

Doug Kelsey, an Austin physical therapist and author, was the first person to really awaken hope in me when I was struggling with a pair of bad knees while living in Hong Kong.

The gist of what he said: Don’t believe pessimistic doctors who say bad knees never get better. They certainly can.

I also uncovered scientific studies showing natural changes in cartilage that indicated the tissue, over a period of several years, showed signs of getting worse, yes, but also of healing. Places in the knee joint that were bone-on-bone often had cartilage filling in the holes when examined by MRI a few years later.

Okay, that’s a bit of a long windup for this New York Times article. The Times was looking at  running and the hoary myth that running is bad for your knees (to be clear, it can be, if you run when injured or don’t train properly).

Ross Miller, an associate professor of kinesiology at the University of Maryland, was involved in a study to try to figure out a puzzle: why, if running pounds knees so hard, don’t more runners develop conditions like osteoarthritis?

He knew that some recent studies with animals intimated that cartilage might be more resilient than researchers previously had believed ... animals that ran tended to have thicker, healthier knee cartilage than comparable tissues from sedentary animals.

The study looked at what would theoretically happen to the healthy knee cartilage of two groups: one would walk six kilometers (roughly 3.7 miles) a day for years, the other instead would walk for three kilometers and run for three.

It’s admittedly a bit confusing to follow what was going on: volunteers were going around a track that had embedded force plates, which measured the impact of running and walking. The collected data was fed into complex computer simulations, that drew on lots of other data too.

Now, here’s the really interesting part, and the Times explanation is a bit confusing, so I'm going to simplify.

There are three possible scenarios for cartilage and how it responds to running:

(1) The cartilage can’t change to adapt to the harsh forces (and therefore would be expected to deteriorate over time).

(2) The cartilage can slightly repair itself after repeated minor damage.

(3) The cartilage can remodel itself and adapt to the intense forces, growing thicker and stronger, just as exercise builds up muscles.

If you were to poll most orthopedists, I bet their beliefs would fall mainly into scenario (1) and (2), but certainly not (3).

Surprise.

If you assume (1) is true, runners have a 98% chance of developing arthritis in their knee joints, the study found. Even if you assume (2), the slight repair taking place isn’t enough to counter the frequent running, and their chances of arthritis decline only a bit, to 95%.

But if you assume (3), they have a 13% chance of eventually suffering from arthritis, which is the same as for the people who were walkers only. This does seem to match up with evidence that the incidence of arthritis among dedicated runners isn’t higher, and may be lower, than for the rest of the population.

The article concludes:

What these results suggest is that cartilage is malleable, Dr. Ross says. It must be able to sense the strains and slight damage from running and rebuild itself, becoming stronger. In this scenario, running bolsters cartilage health.

I can’t say this would surprise me.

I just hope orthopedic doctors see this article too.