Saturday, November 20, 2010

Is Your Knee Doctor (or Physical Therapist) a Structuralist?

And why should you care?

Doug Kelsey, chief therapist at Sports Center, defines structuralism as "a school of thought that believes the genesis of musculoskeletal complaints is from one or more biomechanical abnormalities."

Further, he says:
For patella pain, the biomechanical abnormalities include a laterally tracking patella, weak medial quadriceps, tight hamstrings, tight iliotibial band, tight calf muscles, weak or tight hip rotator muscles and over pronation of the foot. A Structuralist view would then be to set the mechanics "right" and symptoms would subside.
Sound familiar? Pay close attention to that first one: "a laterally tracking patella." That is, in layman's terms, a kneecap that isn't perfectly centered in the trochlea, or the groove that it's supposed to slide through with the greatest of ease. We'll return shortly to that mistracking patella.

So if your doctor (or physical therapist) says your problems are caused by a poorly tracking patella -- or that you must strengthen hip/butt/quad/whatever muscles and stretch the IT band/quads/hamstrings/whatever in order to redress your body's imbalances -- chances are excellent you have a Structuralist.

But does Structuralism make sense as a model to analyze and treat the majority of people who suffer from chondromalacia or patellofemoral pain syndrome? Logically (and instinctively), the answer is no for several reasons.

(1) Can stretching, one of the solutions in the Structuralist toolkit, really correct biomechanical abnormalities? Stretching temporarily lengthens muscle fibers. Then they contract again. How long must you stretch to achieve a lasting, beneficial effect? Answer: it's unclear. Paul Ingraham, massage therapist and stretching skeptic, does quote this therapy-exercise textbook (in his comprehensive online essay looking at how stretching fails to deliver what it promises):
Several authors have suggested that a period of 20 minutes or longer is necessary for a stretch to be effective and increase range of motion when a low-intensity prolonged mechanical stretch is used.
That's a lot of time to devote to a single stretch, for a single muscle, as he notes. Then how often would you have to stretch like that? Once a day? Once every ten hours? Six hours? And, even supposing that stretching can change your biomechanics, how are you supposed to be able to tell when you've reached the sweet spot, of just the right amount of change, and not too much (after all, you don't want to have your patella start tracking to the left because you overcorrected for its tracking to the right, and too much flexibility does lead to unstable joints)?

(2) If the Structuralists are right -- if your biomechanics are at fault -- why do chondromalacia and PFPS usually strike at older ages: 30, 40, 50? Let's look at the commonly blamed factor of kneecap mistracking. If that's to blame for knee pain, wouldn't it become a problem soon after you learn to walk? Why aren't there more three-year-olds with PFPS?

Okay, that seems a bit silly. Let's take a charitable view of Structuralism. Let's say patella mistracking doesn't manifest until the skeleton has finished growing, in the mid to late teens for most people. Fine. Then why isn't there an onslaught of cases of PFPS when people reach their early twenties, as their adult frame finishes growing and their badly tracking patella dooms them to a life of pain?

(3) Finally, here's the big problem with Structuralism, as Kelsey observes: Nobody has perfect biomechanics in the first place. Yet most of us do fine anyway.

Those are three reasons that logically (and instinctively) Structuralism doesn't make sense. But in the world of evidentiary medicine, musings and common sense alone don't constitute grounds for overturning a prevailing paradigm. In the medical world, physicians turn to clinical studies. So let's look at one.

This study ("Patellofemoral Joint Kinematics in Individuals with and without Patellofemoral Pain Syndrome", published in 2006) included three groups: 1. 20 people with PFPS who had clinical signs of patellar malalignment (as evidenced by tests performed during a physical exam) 2. 20 people with PFPS who had no clinical evidence of malalignment 3. 20 people with no knee problems.

An MRI captured images of their knees in various stages of being flexed, to note "patellar motion" as a function of the particular angle their knees were bent. So the MRI could see, for example, whether the kneecap was perfectly centered in the trochlear groove or sliding out to the right or to the left.

If Structuralism was the correct paradigm for understanding PFPS, what would we expect to find? Easy: that the patients with knee pain tended to have kneecaps with the worst tracking.

What the researchers actually found:
No differences in the overall pattern of patellar motion were observed among the groups ... It is clear from the data that an individual with patellofemoral pain syndrome cannot be distinguished from a control subject by examining patterns of spin, tilt, or lateral translation of the patella.
(If you're a Structuralist, that sound you just heard is the floor collapsing beneath you.)

In other words, if you just look at MRIs of how someone's patella tracks, you'll have no idea whether they have PFPS. Someone with a kneecap that tracks perfectly may have PFPS. Someone with no knee pain may have a patella that mistracks. The authors make the point more bluntly in a follow-up letter to the journal where the study was published: "Our findings add to the evidence that patellar mistracking is not a clinically significant factor for most individuals with patellofemoral joint pain."

So there you have it, a crumbling edifice called Structuralism, that your doctor and physical therapist are probably using right now to analyze why you have knee pain and how you should fix it. And is it any wonder that more people aren't healing? And is it any wonder that, in order for me to heal, I didn't need a visit from the angels from above, but rather a cold-eyed rejection of this whole Structuralist approach (I got better through a simple, long process: I strengthened my knees).

So when I ask, "Is your doctor (or physical therapist) a Structuralist?", it's not an idle question. The fate of your knees may hang in the balance.


  1. This blog post made my jaw drop.

    Most doctors told me pretty much the opposite ... That my patella not being in the center was the problem. They said I could consider the lateral release surgery to help recentered the patella but that it has mixed results and that I'd still have to do all the same quad exercises if I did or did not have the surgery for the rest of my life.

    One of my orthopedic surgeons about 5 years ago did tell me that yes my patella was not in the center BUT other people have WORSE patella alignment and yet they have no pain. That really stuck in my head. And yet still at that point did not hit on the way to be cured at that time.

    And more recently, a different surgeon said there was no mechanical reason why I should not be able to get back to an active life. That REALLY woke me up as very encouraging. It was still a puzzle and frustrating why I had so much pain, but to be told it was NOT mechanical (I.e., not the patella listing off to the side that was the problem) made me start thinking about ....well if it isn't mechanical, what is it???

  2. Yes, Knee Pain, I think most doctors tend to be structuralists. But because some are not, it can become confusing, trying to sort out all the advice you receive. Part of my purpose in writing about structuralism is to bring to the fore that this is simply a way of viewing what causes injuries, a framework of analysis if you will, and it may not be correct.

  3. Generally extremely impressed by your work and genuine desire to share your experience with others. I just finished reading your book, a true pager turner for us knee sufferers. I recognized myself in your words many many times.

    On the subject of this post, just to be devil's advocate. Couldn't it be that a younger subject does not experience PFS [yet], because he still has to chew through his cartilage, whereas older people have less cartilage left, hence symptoms appear?
    Another observation related to my situation. When there are no obvious triggers for the onset of PFS, unlike your case where you could clearly trace it back to you aggressive bike hill climbing, would a structuralist view have more credit? do you believe some biomechanical deviation from the norm could cause undue pressure loads on joints which over time result in the wear and tear of cartilage which would originate PFS? Would such hypothesis be true, wouldn't it make sense in addition to gentle continuous motion, to address specific stiffness trough strectching which may resolve the original cause of the cartilage defect? Looking forward to your view.

    1. I may not be as rabidly anti-structuralist as I appear. :) My position is simply that too much blame is placed on structural abnormalities.

      On your first point, yes, I think that's exactly a point that a structuralist would make: that the stresses from a mistracking kneecap won't manifest immediately, but rather over time. If you have a mistracking kneecap, and eventually you have knee pain, a structuralist would say, "See? It finally caught up with you." So if you have a mistracking kneecap and pain, then the malalignment is why, and if you have no pain, well, you just wait (and if you die pain-free you got lucky). So this is basically an argument that's non-falsifiable, like the existence of angels or some such. My thinking is that if the mistracking really is your root problem, it should manifest itself earlier -- it seems suspicious that people can go 40, 50 years then the mistracking kneecap is suddenly a big issue.

      Yes, actually, I do think that some biological deviation from the norm can be significant. Runner A may be constructed in such an ideal way that he can run 200 miles a week; Runner B may have a less ideal structure and may only be able to run 100 without getting shin splints (assuming all else is equal -- their weight, training etc.). But what does this mean? I'd argue it's more about natural limits. I don't think stretching will turn Runner B into Runner A. Also I'm dubious that failure to stretch some tight structure is the real cause of the original injury.

      But on some level, structure definitely matters. If your right leg is 3 inches shorter than your left, don't try to run a 26 mile marathon or you'll really hurt yourself.