Friday, February 11, 2011

What Does "Knee Strengthening" Mean Exactly?

My belief is that, to heal bad knees, you need to focus on strengthening the joint -- that's what's causing you trouble after all -- and forget about obsessing over your leg muscles. (You can build up your quads all you want, until they're as thick as tree trunks, after you fix your knees!)

That's how I succeeded in my recovery, which I describe in my just released book, Saving My Knees.

But what does it mean to "strengthen" a joint? In my case, I had to contend with bad cartilage. An MRI revealed I had "mild" chondromalacia (though I had not-so-mild pain symptoms, so I suspect that the problems lay deeper than the MRI could see). So my mission became to restore that cartilage to better health, to make it stronger. But how?

I began digging around in the world of articular knee cartilage. What constitutes weak or poorly functioning cartilage anyway? Obviously, if it's worn down or damaged structurally, the tissue won't work as well. But then I learned something curious: bad cartilage is generally too soft.

Now here's where things can get confusing. If you cruise the Net long enough, you'll find at least one instance of a doctor pooh-poohing the diagnosis of "chondromalacia," saying that the term makes no sense because it means "soft cartilage," and cartilage is supposed to be soft. That's a rather disingenuous thing to say though.

Because chondromalacia means an "abnormal softening of cartilage." Cartilage is somewhat soft because it must act as a rubbery shock absorber, compressing and then bouncing back to its original shape. Cartilage-as-a-brick wouldn't function too well; a brick has no ability to deform to absorb shock, then recover to its original state.

The issue arises with a kind of excessive and unhealthy softness that (at its extreme) is captured in this delightful bit of imagery from the book Heal Your Knees: "If a man in his eighties tears a meniscus, it wouldn't make sense to try to repair it, because that would be like trying to put stitches in a Boston cream pie."

You don't want Boston-cream-pie cartilage, certainly, that can't hold a stitch -- or bear the burden of a walk up a hill. To better understand why, consider this excerpt from Disorders of the Patellofemoral Joint, by John Pryor Fulkerson (my bold):
Closed chondromalacia is common and may or may not be symptomatic ... it consists of simple softening of articular cartilage, which begins in a very localized area and then extends progressively in all directions ... softening, which may at times appear fluctuant, may be present in varying degrees of severity, from simple softening to a more advanced form in which a type of "pitting edema" can be observed after digital or blunt instrument pressure. This loss of elasticity, which this softening represents, decreases the function capacity of cartilage and explains the reaction of adjacent subchondral bone to which the compression forces are transferred abnormally.
There we go. That supplies the needed clarity. Soft = loss of elasticity. Loss of elasticity = not very good shock absorber. Since cartilage's key role is to lessen shocks/forces transmitted through the knee joint, too much softness means lots of problems. Plus there's this to consider: soft tissue is more prone to flaking, fraying and tearing. Flaking off bits of cartilage can be a source of pain, as they migrate through the synovial fluid to the nerve-rich synovium. And I hardly need to belabor the point that you really want to avoid tearing your cartilage.

So my calculus was simple: I didn't want to prematurely have Boston cream pie (or anything resembling it) in my joints. That meant I needed to strengthen and stiffen my knee cartilage (here I'm talking about indentation stiffness, and not brittle stiffness), through a long program of high-repetition "exercise" that gradually increased in intensity.

I knew that approach could work, from a Swedish study ("Positive Effects of Moderate Exercise on Glycosaminoglycan Content in Knee Cartilage"). Moderate physical activity boosted the content of glycosaminoglycans (GAGs) in the cartilage of participating subjects. Having more GAGs in your cartilage is great; they contribute to making the tissue healthier and more resilient.

So for anyone trying to understand how I healed, that was one important, basic insight. I knew my cartilage was weak/damaged/soft. And I knew I had to make it stronger.

And I did, and by doing so, strengthened my knees.


  1. I'm really interested in this topic. I'm curious about the repair capability of severely damaged cartilage. I had a microfracture procedure in my left knee. My symptoms were primarily mechanical -- my kneecap would catch painfully every time I moved it through a certain angle.

    When I got the pictures from the arthroscopy, I noticed that the damaged cartilage almost looked like hair. It looked "fuzzy", with hundreds of tiny strands that had clearly been torn apart. It's hard to describe unless you've seen pictures of it. Mine was worn down to the bone in places.

    Do you think cartilage damage of this type can heal naturally through gentle movement? I'm having trouble imagining the mechanism that could promote healing in this case. The chondrocytes are captured in their lacunae, presumably within the loose strands of visibly damaged cartilage. How can they possibly "capture" the free-floating ends of the torn fibers in order to reattach them? I guess I'm having trouble understanding the mechanism that would allow badly damaged or torn cartilage, as is seen in Outerbridge grade 3/4 lesions, to heal. It's easier to understand how it might work in earlier-stage chondromalacia where the cartilage is still contiguous but is soft and has stopped providing adequate shock absorption.

  2. Anonymous, you're obviously doing the extra-curricular reading! Some good questions ... here are the quick answers: (1) Yes, I do think cartilage damage of this type can heal through the right kind of gentle movement. (2) I don't think the existing cartilage does capture the fibrillated strands (and yes, I know what they look like, and suspect that's what I had in my knees).

    I started to write out a reply to your comment, but it began getting way too long in my head, so I'm going to do a blog post this weekend answering you in more detail. Just look for it then. Thanks for the comment.

  3. I'll look forward to it. Like you, I must have read at least 50 papers in Orthopaedic journals and textbooks when I was trying to decide whether to have surgery. By the way, I really enjoyed your book and I read the blog daily. I ran with one of your ideas -- I keep a small stationary bike under my desk at work. It will actually turn itself if it is plugged in and I've been using it as a poor-man's CPM to enable me to get lots of gentle joint motion throughout the day. I've only had it for a couple of weeks now, but I think it might be helping somewhat.

  4. Anonymous- can you give me more information on this bike? What is it, where did you get it?

  5. Can you provide more information on this small, stationary bike in the office? I am in so much knee pain and have visited 6 orthopedic doctors with no real solution for my problems - chondromalacia patella and fractured cartilage.

    I am looking for information on how to strengthen knees and rebuild the cartilage.

  6. I think the bikes are like this (though I'm not advocating this particular model). Some I've heard can be flimsy/unstable, so you may want to watch out for that: