Saturday, June 15, 2013

What Implications Does “Envelope of Function” Have for Designing a Plan to Beat Knee Pain?

Last week I described Scott F. Dye’s common-sensical idea of the “envelope of function.” He believes that patellofemoral pain patients should try to “maximize the range of painless loading for a given symptomatic joint (envelope of function) as safely and predictably as possible.” Such an idea is consistent with my own belief in slowly strengthening a damaged joint.

This week, I want to consider implications of the “envelope of function” perspective. In other words, how does it translate into practice?

At the end of this post, I’ll tell you what Dye himself recommends for treating achy knees.

Before that, I want to share my own observations about what “envelope of function” implies.

But even before that, it’s worth taking a few moments to examine which popular theories Dye rejects as insufficient to explain knee pain. Doing so helps explain what compelled him to develop his analytical framework in the first place.

Dye, a long-practicing orthopedic surgeon, surveys current approaches to handling patellofemoral pain with more than a touch of dismay. What he sees are theories that often lead to “corrective” surgery that is worse than ineffective; it actually harms the patient.

For one, some in his field are obsessed with cartilage to the point that they try to fix damaged tissue through chondroplasties and microfractures. (Note: here my thinking somewhat diverges from his, on the role of bad cartilage in contributing to knee pain, but that’s a long digression -- in any event, I think he’s right that much surgery is unnecessary).

As Dye observes, the level of pain a patient experiences doesn’t always correlate well with the degree of chondromalacia in the knee. You may have advanced chondromalacia and no symptoms, or articular cartilage that appears normal that’s associated with a very painful joint (all true, but I think the total picture is a bit more complex).

Dye also rejects the “malalignment” school of thinking (what I have often disparaged as “structuralism”), which commonly blames knee pain on an improperly tracking kneecap. He gives several reasons why this analysis doesn’t make sense.
If the presence of observable factors of malalignment is so important ... why does one find patients with bilaterally radiographically determined patellofemoral malalignment [that is, mistracking in both knees as indicated by X-ray], with only unilateral symptoms [that is, symptoms in only one knee]?
Or there’s this to ponder:
Why do more than 90% of patients with anterior knee pain who have a diagnosis of malalignment as the cause have a successful response to conservative therapy, even though there has been no documentation of long-term restoration or correction of the supposed causative underlying indicators of malalignment.
Finally, he points out:
The malalignment theory also does not explain the variability of patellofemoral symptoms in the same patient at different times, including the presence of sharp pain on occasion and then dull aching pain on another.
He does recognize that “some patients have clinically significant malalignment” that responds well to corrective treatments, such as a lateral release. “However,” he goes on to caution, “in my experience, the numbers of these patients are relatively few.”

Finding the blame-the-cartilage and blame-the-malalignment frameworks for understanding and dealing with knee pain wanting, he comes up with “envelope of function.” But what does this perspective imply, in practical terms, if you’re trying to fix a couple of bad knees?

Here are what I consider two interesting implications:

“Envelope of function” is kind of a big tent idea. That is, you can interpret it as being somewhat agnostic about the origin of knee pain. What matters, a believer could argue, is the fact that you have a certain degree of knee pain and, given that, what’s the best way to heal?

For example, I thought my pain stemmed from cartilage problems. Maybe I was right. Maybe I was wrong. Arguably, an “envelope of function” approach works in either case because, primarily, your concern is staying within the range of loading that your joint can tolerate.

Obviously, this concept wouldn’t make sense for a patient who has an important, identifiable contributor to knee pain that must be dealt with before healing can occur -- the equivalent of an iron spike sticking out of the joint that must be removed first. But I don’t think that describes the vast majority of patients who have chronic knee pain.

An “envelope of function” approach suggests it’s absolutely critical to determine that range of optimal loading for your bad knee. The best place to do this, in my opinion: at a doctor’s or physical therapist’s office, using machines/devices that can quantify exactly how much load your knee can safely tolerate.

Yet very few medical professionals attempt to do this. This is one reason I think we’re still in the Dark Ages on treating chronic knee pain. The American military can fire a cruise missile down a chimney 1,000 miles away, but the U.S. medical establishment can’t (or has no desire to, more significantly) measure how much force an individual can safely put on a bad knee joint, over the course of a 24-hour day.

Now, what does Dye himself recommend for patellofemoral pain patients, besides a “scrupulous adherence to load restriction within the patient’s reduced envelope of function”?

An anti-inflammatory program.

He appears to favor icing and medication, and approvingly cites a regimen of icing 15 to 20 minutes, two or three times daily.

Indeed, runaway chronic inflammation -- the undesirable kind -- is a problem among those who have constant knee pain. I’m a little leery of his solution though, as I usually associate icing and medication with people who use both to keep doing unhealthy things (such as running when their knees aren’t strong enough). Also, icing and medication interfere with the signaling you get from your knees that’s often telling you, “Stop doing that!” (sitting, standing, whatever)

Still, anti-inflammatories may be a good idea, if used smartly.

He also supports painless (his emphasis) muscle strengthening, stretching and patellofemoral taping.

My own opinion (as I’ve made clear on this blog): stretching isn’t of much use but if it feels good why not?, muscle strengthening should be put on the back burner completely in favor of “joint strengthening”, and as for taping -- sometimes it can offer relief, so why not try it as an interim measure?

“A period of 6 to 9 months of conservative therapy often is required” to improve an ailing joint, Dye informs us soberly, then warns: “The first pain-free day does not mean that the envelope of function has been fully restored but that healing is occurring.”

Getting to the right healing program isn’t easy, as Dye observes. “It is not unlike trying to find the numbers to a combination lock.” True, so true. However, when you succeed in finding the right sequence that springs that stubborn lock, and get squarely on the long-term path to getting better, it’s really a great feeling.


  1. One interesting thing is that even when he talks about muscle strengthening, he talks about mostly quads. He doesn't talk at all about hip and glutes. This seems to agree with the concepts we discussed earlier in the year. No harm in strengthening them if it doesn't hurt the knee and doesn't cut into your time dedicated for healing the knee.

    I like the emphasis on icing. I personally have found that ice is a big help, but I only ice once per day or sometimes two. So, I'm going to try 3-4 times per day to see if that can make a difference. I've got a way where I can
    Prop my leg up at my desk at work, so, I can even ice during business hours.

    It was interesting that he does recommend muscle strengthening but emphasizes to do it only as much as it doesn't hurt my knee. He doesn't mention the delayed pain response though-- at least I didn't see it.

    Also interesting is that he feels the benefits of taping the patella is mainly for relief ( keep the patella from rubbing on a swollen area and causing further swelling) as compared to trying to "fix" a mis-alignment problem.
    I feel that "stretching" is basically the same idea. Not so much promoting healing, but provides temporary relief from the patella being tugged into inflamed areas.

    Very interesting that he emphasizes that each patient has to find what works for his own situation and says it's like trying to find the numbers to open a combination lock. Really great visual!

    And this articles emphasis on not having surgery made me greatful that the two OS I saw within the last 7 months both strongly recommended I continue trying physical therapy as opposed to surgery.

    1. I re-read my above comment and I see I didn't complete my thought about the hips/glutes. What I meant to say is that the article seems to support what we discussed earlier which is that although there's no harm in strengthening hips/glutes if I doesn't hurt the knee, do not look to hip/glute strengthening as a key to solving PFPS.

  2. First posted here a year ago, six months after a failed chondroplasty with lateral release that was performed in the effort to treat a catch behind my left patella. Had been casting about in desperation while looking for answers and discovered Richard’s book, which addressed, among other things, issues I was having with the negative loop of PT: PT was aggravating my already angry cartilage. Also, I liked the idea that I could “save my knees.”

    Am looking at my post-surg "scope-shots" as I write this. Can see the pic where a huge chunk of crabmeat was “shaved” from my patella. One year ago after limping in on my non-functional, atrophied leg for a follow-up visit, that OS wrote in his report that the knee was healed and that I had a chondral defect (his gift to me?) and that my current difficulties were a natural expression of my arthritic degeneration. I was on my own.

    Have made some discoveries over the course of this last year of rehab. My right knee is now doing much better. Like Triagain I had developed severe bi-lateral PFPS post-surgery, but my chondromalacia (PFPS) is currently much improved. My situation is complicated, in part due to the above mentioned deep chondral defect. But this too seems to be SLOWLY healing. If Richard is right and chondral defects can heal, healing this defect will take many more months and possibly years. Finding my “envelope of function,” because of the complicated and varying nature of my injured knee(s), is difficult and is an always moving target. I also may have scar tissue and it is my belief that to break scar tissue up you have to push the envelope out to the edge and just a tad beyond from time to time.

    Read Richards response to "Triagain" and reread those posts on breakdown points and want to add a few comments. I agree with Richard’s analysis with my experience being like his, as I abused my body: 49, racing pro 1/2, master 30+ 1/2, riding 100 milers, sometimes twice a week, climbing 2000' x 3 for interval work, riding sick, in rain, sleet, snow, etc., while dehydrated, ignoring pain… the whole stupid catastrophe. But I also suspect that there are additional systemic and profound contributing factors to cartilage degeneration. One of those factors is general stress. At the time of my initial injury I had a lot on my plate. I also suspect that a contributing factor to softening cartilage is diminished immune response, the origin of which is itself probably as rife with varying risk factors as bad cartilage. Studies have shown that knees with OA have greatly diminished or outright lack the chromatin protein HMGB2, which (if I understand correctly) is responsible for cartilage cell division and regeneration. My guess is that HMGB2 dies off for at least 2 possible reasons: One, structurally induced die-off: fissuring leads to joint swelling, leads to more fissuring with joint inflammation/fluid further attacking cartilage, which minus HMGB2 is not replenishing. The other type of die-off is stress/immunologically related. Yes crazy hypothesis (some scientist out there test it for me please!), but sawing leg bones in half to place exotica seems nutty too, particularly if you can save your knee. That said, I think that immune response can be addressed (in the least, the whole response is another post) with a high quality, enterically coated probiotic. ( I suggest Dr Ohhira and Brenda Watson's brands) and with a balanced diet. Something like 85% 0f the immune response is in the gut (read DR O. and Brenda W.'s explanations for guts gone bad). Sorry for the long post. I believe info to help people heal should be free. I am not trying to sell anything.

    Thanks for your fine ideas and posts Richard and for offering a venue for the collective experiment to heal cartilage.
    Hope this helps more than it hurts. Good luck to everyone trying to healing their knees.

  3. Now I've gone through the two articles by Dr. Dye more carefully. I nod my head vigorously when I get to many of his points. Yes yes!

    My main point of despair comes in the Theraputic Implications article when he talks about "painless muscle strengthening" on page 309 at the end of paragraph 1 "the absence of pain is the best indication that the involved structures are not being damaged." no no no! Well, I mean at the superficial level, yes, one certainly does not want to be in pain while doing the muscle strengthening. But. That's not the part where the despair comes in. The hard part is the delayed pain effect. So, you faithfully do the painless exercise and you think you are doing the right thing to help your knee, but then 24 hours later the knee has a flare up, which sets you back 1-3 weeks. :(

    So if I could write to Dr Dye I would urge him to talk about tracking your pain levels so you can determine if a "painless exercise" truly was or was not damaging the knee joint.

  4. Racer X, that is interesting about the probiotic immune response stuff. I may try that along with an anti-inflammation type diet. As you can tell by my too frequent posts, I'm really struggling with my knee, but I'm hanging on.

  5. Knee Pain - I never had the stabbing sudden pain, mine is aching & burning/stinging. Ice definitely helps mine too, but like you i've only tried icing 1-2 times/day, not multiple times. I've also just discovered flying economy class from Aus to the UK is murder! Like you, my knees often feel quite good during exercise, but I pay for it in the hrs after, hence tricky to gauge the envelope of function.

    Racer X- your situation sounds v similar to mine, I suspect hard big gear windtrainer intervals were my downfall, plus riding in sub-zero temps. The immune system/probiotic issues is interesting, might have to try those. What else have you done to improve your situation (e.g. did you give up riding/training/racing???)


  6. This blog is full of liars and miscreants.

    1. can you give us more insight? I would apprecciate if you have another approach or solution