Friday, February 18, 2011

Comment Corner: Can Even Badly Damaged Knee Cartilage Heal?

Before the regularly scheduled programming begins: If you've read Saving My Knees and enjoyed it, please drop by the book's Amazon page and post a review. There's no crack team of publicists working the phone for this book -- I'm relying on good old-fashioned word of mouth.

Now here's the second installment of "Comment Corner" (okay, it's a bit hokey as a name), in which I answer a reader comment at some length. Buckle your seat belts; this one is a bit of a long ride!

Last week I was talking about strengthening the knee instead of the surrounding muscles, and exactly what that means. That prompted this comment:
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.
Good questions. I recognize a kindred soul, trying like crazy to figure things out, as I once was.

First, normal cartilage looks like this (images borrowed from Nice and smooth, like a baby's bum:

Then you have "horror show" cartilage. Degenerated, fibrillated, like a fright wig:

Yow! No wonder knee pain patients staring at photos of their scoped joints feel a sickening little roll of the stomach. How the hell does image #2 ever improve and turn back into #1? That would seem about as unlikely as your broken vase, lying on the floor, jumping up and spontaneously reassembling itself.

Okay, let's look at the prospects for healing bad cartilage -- really bad cartilage that looks like a hairy crab. We'll do this in two parts, because there's Stuff I Know and then Stuff I Think Might Be Right.

Stuff I Think Might Be Right

So how does this "cartilage hair" reattach itself, as Anonymous wonders, to make your cartilage whole again?

Thought experiment: Imagine taking a cheese grater (don't really do this!) and barking it a few times, quite roughly, against the skin on your forearm. What's your arm going to look like after you finish? Probably you'll have a lot of little pieces of skin hanging off.

How does this skin then reattach itself to make your skin whole?

Answer: It doesn't, of course. The irregular bits eventually fall off. Over time the surface of your skin heals.

My guess is that something similar probably happens with raggedy cartilage that succeeds in healing. In fact, my best theory of what was going on with my joints -- I had a lot of problems though an MRI detected only "mild" chondromalacia -- is that I had some of this "cartilage hair," at least in certain places.

Now if I'm correct, the "cartilage hair" is just going to flake off. You have to accept that. Further, as it does, little bits of cartilage detritus will migrate to your synovium and make your knee sore. That, too, you have to accept.

What you have to focus on is the underlying cartilage that's intact: That stuff is too soft. It is in prime "hair-making" mode. It will eventually fissure too, turn into synovial seaweed, and go the way of its surface brethren if you do nothing. Which is what a lot of people do: nothing.

The intervention I believed was necessary: strengthening and stiffening the existing cartilage, very slowly. While this process occurs, there will be some pain associated as the bad stuff flakes off and migrates away through the joint. But you need more resilient tissue and the only way to get it is through motion coupled with appropriate load (a big hat tip to Doug Kelsey!).

You may be wondering: what about the chondrocytes (cellular cartilage-making factories) that are trapped in the "cartilage hairs." My guess is they go bye-bye. But if that unduly stresses you (I can tell Anonymous is doing the "extra-curricular reading" and is aware that chondrocytes are not that plentiful to start out with, scattered throughout the tissue), these cells have apparently shown an ability to regenerate.

This is from a prolotherapy Web site -- I'm not saying I'm a fan of prolo, or that I agree with everything on this page (though much of it makes sense), but the cited study is paywalled so I can provide only the prolo summation:
... data suggest that under circumstances of chronic injury, such as is seen in osteoarthritis or trauma, chondrocytes are capable of mounting a significant reparative response and can replicate their DNA to form new cells.
Okay, the above is Stuff I Think Might Be Right. Anyone with more knowledge/insights, please weigh in. Now for:

Stuff I Know

I know that cartilage doesn't have to heal completely, to pristine condition, in order for knee pain sufferers to escape their torments. Most of the population over 30 has some damaged cartilage in their knees. So first thing: the bar you have to jump over is lower than you may think. You don't need normal cartilage again, just cartilage that functions well and doesn't hurt.

I also know that very damaged cartilage has been shown to heal over time. I think the scale being used in studies I've read has been on ICRS grading, not Outerbridge, but if you look at these photos here, the two are similar (e.g., an ICRS Grade 3 is basically an Outerbridge III).

Here are some interesting numbers from a report published in Rheumatology magazine in 2006 entitled "Factors Affecting Progression of Knee Cartilage Defects in Normal Subjects Over Two Years."

Initially, there were 14 locations at Grade 3 (less than 50 percent thickness) in the subjects' knees. Three remained the same and five went to bare bone -- that's the bad news. However the good news is that almost half of them improved: four became Grade 2 and two Grade 1, which is nearly normal!

There were five sites at Grade 4, or bare bone. Now you'd expect at the end of two years, those five sites would still be at Grade 4, absent surgical intervention (such as a microfracture). But one ended up Grade 3, two were Grade 2, and one even healed all the way to Grade 1!

I'm willing to bet that, if these knees with Grade 3 and Grade 4 lesions had been scoped, you'd see plenty of that "cartilage hair."

So far I'm telling a wonderful story, but caveats are in order.

As careful readers no doubt noticed, these were normal subjects. Also it's not clear how big their lesions were. Still, I think the big takeaway is that cartilage can heal, even when you've got no more than exposed bone to work with. That's a really great, inspiring message.

If you're Anonymous, though, what you face is fairly challenging. You've got to give your knees enough motion, and the proper amount of load, without blowing them out, so to speak. This will not be easy. This will take a lot of time, I bet (maybe four or five years).

But, if you can see yourself gradually getting better over that long stretch, it's certainly better than the alternative: resigning yourself to a life of constant pain. Remember, there's always hope.


  1. This is an excellent blog post. I will now re-read it several times.

  2. Agree! I was diagnosed with a grade4 of the patella via an MRI six months back, and this post gives me hope. I've been riding my bike religiously ever since, and have made significant gains. -Erik

    1. I have been diagnosed with Grade 3 via MRI two weeks ago. Very Shocked. Other knee fine. Will follow Richards advice - and accept a long slow path to recovery. Mike

  3. Can ligaments regenerate themselves