Sunday, August 15, 2010

Yes Virginia, Damaged Cartilage Can Heal

In my blog "mission statement," if you will, I set out four beliefs about how to treat bad knees that I think are wrong, but that are also (unfortunately) widely held by physical therapists and medical doctors. In this July 3rd entry, I expanded on why I think this particular statement is false:

A plan to heal bad knees should focus on strengthening the quadriceps muscles.

This dictum fails the common sense test, as I noted. Your quadriceps don't hurt. Your knees hurt. If your knees are the problem, why not not make them the focus of the treatment? Why not try to strengthen your knee joints?

This seems so obvious that you have to wonder, "What's the catch? Surely, thousands of smart physical therapists and doctors wouldn't blindly ignore a course of action that appears so logical. There must be some explanation for why they don't try to strengthen the joints."

Yes, and that reason is probably this other wrong-headed belief:

Damaged knee cartilage doesn't heal; at best you can prevent it from getting worse.

This is what your physical therapist probably believes (though, in the interest of keeping up your spirits, most likely doesn't speak aloud). Given that belief, quad-directed treatments make more sense. After all, if damaged knee cartilage can't heal, then maybe the best hope is to try to bulk up the muscles around the knee, so that they can cushion the joint from harmful impacts. (Ignore, momentarily, the paradox that with a very weak joint, you can't build up the muscles without further breaking down the joint itself.)

Suppose though that damaged knee cartilage stands a reasonable chance of healing.

Then the whole ball game changes. Then ignoring the joint in favor of the muscles seems downright foolish.

The scientific evidence, in fact, does show that knee cartilage apparently can heal. Now, if it healed at a very low rate -- say, a percent or two of all cases -- then you still might hesitate to embark on a program to strengthen the joints, because the odds of success would seem too low.

But it turns out, the rate is considerably higher.

Like 37 percent.

Here's the evidence:

A study conducted in 2000 by researchers in Southern Tasmania used MRIs to assess the knee joints of 325 subjects, to detect changes over a two-year time span. They found that 33 percent of the subjects had a worsening of cartilage defects in one of their knee compartments, but 37 percent had an improvement!

Note: these subjects whose cartilage got better weren't on any special exercise program, or taking any special supplements, or receiving any special kind of treatment. They were, for the most part, simply people going about their lives -- some had knee pain and some didn't, some probably exercised and some didn't -- and almost two in five had the condition of the cartilage in their knee joints improve.

(Actually, in a future entry, I'll show you why the rate was almost certainly higher than 37 percent. But that proof involves a little deep thinking, so I'll reserve it for a later entry, to keep these blog postings short.)

So next time your physical therapist says (or implies -- they don't really come out and say it), "Well, we have to focus on the muscles, because the cartilage can't heal," you should say, "And what do you base that on?"

Because this one study -- and I've got two others I could cite as easily -- shows that cartilage does appear to heal. So not only does it make sense to strengthen the joint because that's the source of the problem, but also because a key tissue in the joint -- the cartilage that is the critical shock absorber for your knees -- can get better.


  1. I think it makes sense that strengthening your quads will take some of the impact from walking or running away. It is like a knee brace.

  2. One of the problems with this dichotomy is that 1/3 of the time the damaged cartilage heals, 1/3 it stays the same and 1/3 of the time it gets worse. Why?

    That's the needle in the haystack.

  3. Yes, that's interesting, but I think it's a solvable mystery (if someone were to design the right kind of study). Remember, the study cited above was a natural study -- the researchers weren't trying to set up hypotheses beforehand to see if they could figure out what led to cartilage healing or what led to it getting worse. They were just interested in seeing how it changed over a couple of years, then trying to find links between age, sex and BMI and the observed changes in the tissue.

    The banner news of this study is that, for more than one-third of the subjects, the cartilage defects improved in one of the compartments in their knees over two years. If you asked a lot of doctors how often cartilage healed in knees, I bet they'd guess something closer to 2 or 3 percent (not 37). So good news!