I am a science writer and a former Registered Massage Therapist with a decade of experience treating tough pain cases. I was the Assistant Editor of ScienceBasedMedicine.org for several years. I’ve written hundreds of articles and several books, and I’m known for readable but heavily referenced analysis, with a touch of sass. I am a runner and ultimate player. • more about me • more about PainScience.com illustrations by Paul Ingraham,
Welcome to the most detailed guide to patellofemoral pain syndrome on the Internet. This tutorial goes as deep into the topic as you can go. Every anterior knee pain base is covered: what it is, how it works, the myths and controversies, diagnostic help, worst case scenarios, analysis of every possible treatment method.
Patellofemoral pain syndrome (PFPS), also known as runner’s knee, is the most common of all kinds of knee pain, causing pain around and under the kneecap. Almost anyone can get it, but it particularly affects runners, cyclists and hikers, and also office workers or anyone else who sits for a living. It’s also common in teens. Almost 40% of pro cyclists will get anterior knee pain in any given year,1 but runners are by far the most numerous victims, and PFPS is the most common of all runners’ knee injuries.2
I survived a brain tumor. Knee rehab has been worse.
~ a reader
Knee pain may be common, but it’s surprisingly hard to find good self-help information for it. Patellofemoral pain is one of the most misunderstood of all knee pain problems. There are countless shallow webpages about it, but most just repeat the same points of oversimplified conventional wisdom.3 And not many doctors and therapists are prepared to treat tough cases.
About footnotes. There are 242 footnotes in this document. Click to make them pop up without losing your place. There are two types: more interesting extra content,1Footnotes with more interesting and/or fun extra content are bold and blue, while dry footnotes (citations and such) are lightweight and gray. Type ESC to close footnotes, or re-click the number.
and boring reference stuff.2“Boring” footnotes usually contain scientific citations from my giant bibliography of pain science. Many of them actually have pretty interesting notes.
Getting good care for patellofemoral pain is a challenge
Many popular treatments for PFPS are of dubious value:
Correcting muscle imbalances is by far the most common prescription for PFPS. The idea is to teach muscles to pull more evenly on your kneecap — which good science has shown to be difficult at best, possibly impossible, and quite likely irrelevant.4
pro Strong enough for a pro Although made for patients, this tutorial is advanced enough for physicians and therapists. Many footnotes contain extra information and references.
Yes, I do criticize common practices and conventional wisdom! Let me know if you disagree — I often make changes based on feedback. See my professional reading guide.
Quadriceps massage is a popular alternative treatment, but massage — while good medicine for many painful conditions — is really not very helpful for kneecap pain, which is a very “jointy” problem.
“Stay active” is one of the most common recommendations — but it can be the worst therapy of all for patellofemoral pain. It’s just knee jerk advice, given by professionals unfamiliar with the nature of PFPS. While exercise can be useful, “staying active” is overly simplistic advice, and can seriously backfire.
Treating PFPS like arthritis is a basic misunderstanding of the condition. Family doctors usually do this, but they are generally poorly informed about PFPS.5 It’s an understandable mistake — the distinction between PFPS and arthritis is complex — but it’s bad news for the patient with serious chronic pain!
Knee surgery is rarely a good option and often prescribed prematurely. Specialists6 and orthopaedic surgeons cannot be counted upon to provide good advice for PFPS.7 Experts believe surgery to be quite risky,8 and the research is very discouraging.
You should try to find good professional help, but it’s a great idea to be as well informed as possible when you do it, or you can easily waste a lot of time and money on dubious therapies — even if this tutorial can’t give you “the answer,” I hope it can at least help you avoid ineffective treatment.
How can you trust this information about patellofemoral pain?
I apply a MythBusters approach to health care (without explosives): I have fun questioning everything. I don’t claim to have The Answer for patellofemoral pain syndrome. When I don’t know, I admit it. I read scientific journals, I explain the science behind key points (there are more than 250 footnotes here, drawn from a huge bibliography), and I always link to my sources.
I don’t offer a miracle cure because (duh!) there is none! It’s important to state this clearly. Wouldn’t it be great if there were a proven treatment with minimal cost, inconvenience, or side effects? But medical science is nowhere close to this for most chronic pain conditions, and especially for patellofemoral pain.9
However, there are good reasons for optimism.
I can explain all the options, help you to confirm your diagnosis, and debunk bad ideas. It may or may not lead to a “cure,” but it will get you as close as you can get. Some readers will finally break free of their patellar pain. Others will make progress after ditching a counter-productive therapy, or trying an option they didn’t know about before. And maybe that is kind of miraculous! But probably not!
A quick overview of patellofemoral pain
PFPS affects the kneecap and surrounding area. Don’t confuse it with iliotibial band syndrome (ITBS) which definitely affects primarily the outside of the knee (the lateral or outward-facing side of the knee). This picture is of a right knee.
Patellofemoral pain syndrome (PFPS) is a problem with pain that feels like it is mainly on the front of the knee, specifically on the underside of or somewhere around the edges ofthe kneecap.[Wikipedia] One or both knees can be affected. The pain is usually worse when climbing stairs or hills, or after sitting for a long time.
In average cases, the pain is not severe and the problem often goes away with basic physical therapy.10 “Basic physical therapy” probably isn’t actually effective, but recovery proceeds anyway simply because the body is pretty good at healing.11 But many cases get worse instead of better. For the unluckiest patients, “basic therapy” completely fails and patellar pain becomes permanent and almost crippling.
Honest professionals know that the causes and cures for patellofemoral pain syndrome are unknown. But most doctors and therapists buy into the conventional wisdom: that the problem is essentially “mechanical.” Unfortunately, those theories have serious errors that are rarely discussed. Fortunately, a few medical experts suggest good alternatives, which will be explained in detail in this tutorial.
What’s in a name? The many labels of patellofemoral pain
“Patellofemoral pain syndrome” is a surprisingly meaningless name. It basically means “strange kneecap pain,” but in Latin. “Anterior knee pain syndrome” is another common name with an even broader meaning, and it’s a little more direct and honest: it’s pain, and it’s on the front of your knee, ‘nuff said.
Sometimes the “pain” part is dropped and it is just called “patellofemoral syndrome” or PFS.
The words “patellofemoral pain syndrome” are often used as a catch-all diagnosis in practice, without any diagnostic certainty — they may refer to nearly any pain roughly on the front of the knee, which may have any of several possible causes, none of which are particularly clear. Technically, it’s a diagnosis of exclusion — what’s left when everything else has been eliminated.12 The problem gets “syndrome” status because of this lack of clarity, and the fact that this particular kind of joint pain is so common.
Do you live in a chair?
“Chair warriors” who spend more than 4–6 hours per day suffer as much from knee pain as many runners. Woe to you if you both run and work in a chair …
“Runner’s knee” is a popular description among runners, of course, and they do get it more often than anyone else. But it is not a good term to use, because there are at least a half dozen other conditions that could be meant by it, especially iliotibial band syndrome. And of course it excludes other people who get the condition — all those people with cyclist’s knees and hiker’s knees, for instance!
Runners get anterior knee pain more often than anyone else.
Calling it “runner’s knee” particularly leaves out people whose knees hurt while sitting and because of sitting. Office workers and other chair-bound workers really do suffer from PFPS in droves. In fact, another name for this condition is moviegoer’s knee because of the tendency of the condition to cause pain after sitting for a long time. This also explains the use of the term “theatre sign” among professionals, as in, “He’s got theatre sign — must be a case of movie-goer’s knee.” In my professional experience, however, you could just as well say, “He’s got desk job sign — must be a case of office worker’s knee.”
One more naming note: occasionally you’ll hear therapists or doctors call this condition “patellofemoral tracking syndrome” (PFTS) or even chondromalacia patellae (definitions coming soon), but these are blatantly in error: these are things that might be causes of the condition, but they are not the condition itself.
About patellofemoral pain in teens
Patellofemoral pain in teens isn’t specifically covered in this book. However, the book is still useful for young patients.
The incidence of patellofemoral pain in adolescents is only a little bit higher than it is in the general population, and it is generally less serious and stubborn. It is mostly a temporary condition: they recover from or grow out of more easily than adults do. Although serious cases certainly can and do occur in teenagers, their age is not particularly relevant to those cases. A serious case in a teenager has to be handled in pretty much the same way that you would handle a serious case in an adult. So although age is a factor I haven’t focussed on, everything that I have focussed on should be of interest to teens with persistent knee pain.
Nature of the Beast
The (many) possible causes of patellofemoral syndrome
Officially, no one knows what causes it. Here is an entertaining selection of typical disclaimers from some scientific papers dating back to 1988:
Back in 1988 Potter et al. summed it up: “Ironically, as simple as its presentation is, lack of consensus on the fundamental factors associated with PFS remains. No agreement exists on the exact pathophysiology ….”
In 1993, the Clinical Journal of Sports Medicine published an editorial called “The myth, mystic and frustration of anterior knee pain,”13 a title that certainly reveals a degree of medical uncertainty on the subject!
You would hope for progress over the next few years, but in 1998 Journal of Orthopaedic & Sports Physical Therapy published the opinion that “there is no consensus on the most effective method of treatment … the indications and contraindications of each approach have not been well established … [and] there is no generally accepted classification scheme for patellofemoral disorders.”14
Not long after, in 1999, the journal American Family Physician, in one of its excellent physician tutorials, said that “Managing patellofemoral pain syndrome is a challenge, in part because of lack of consensus regarding its cause and treatment,” and “no single biomechanical factor has been identified as a primary cause of patellofemoral pain.”15
And things haven’t really improved. In 2006, with resounding negativity, Näslund declared that “no consensus on the definition, classification, assessment, diagnosis, or management has been reached.” So, no consensus on anything — wow — and that is still true to this day.
That’s the official, reasonable position. Any honest doctor or therapist should be happy to admit that almost everything about PFPS is basically a mystery. But in practice, most doctors and therapists think and act like the conventional wisdom is adequate.
The conventional wisdom
I’m pleased to say that American Family Physician came around. They say that the mystery of PFPS has been solved. (It hasn’t really, of course. I’m being sarcastic.) In a tutorial for physicians published in 2007, they confidently declared the cause of PFPS:
[Patellofemoral pain syndrome] is caused by imbalances in the forces controlling patellar tracking during knee flexion and extension, particularly with overloading of the joint.
Well, thank goodness! That’s nice and clear, isn’t it? The conventional wisdom says that patellofemoral pain syndrome is painful degeneration of the cartilage on the underside of the kneecap, caused by a “mechanical” failure of that joint. What kind of failure? A “tracking” problem, in which the patella doesn’t slide evenly in its groove or “track” on the femur. For this condition, we need yet another multisyllabic name: “patellofemoral tracking syndrome.”
Another syndrome? I’m afraid so. It even has almost the same acronym: PFTS instead of PFPS. The conventional wisdom is so entrenched that many professionals consider the “tracking” syndrome to be virtually synonymous with PFPS itself.
The conventional wisdom is so entrenched that patellar “tracking” syndrome is virtually synonymous with patellofemoral pain itself.
But the idea that tracking problems cause patellar pain has not been proven beyond a reasonable doubt. In fact, as I will show in the sections ahead, it’s incredibly difficult to even prove that these problems even coexist, let alone how much they have anything to do with each other … if anything at all. Even stranger, it turns out that tracking problems are extremely difficult to even identify, let alone blame for anything. And as if this wasn’t enough trouble for the conventional wisdom, it turns out that even the “degeneration” of the kneecap’s cartilage is a scientific myth … a myth that probably has little or nothing to do with patellofemoral pain syndrome!
Wow. That’s a lot of myths.
The evidence that tissue pathology does not explain chronic pain is overwhelming (e.g., in back pain, neck pain, and knee osteoarthritis).
And yet! Pain in the patellofemoral joint mostly does not appear to be associated with any identifiable tissue degeneration or damage, dysfunction or malfunction, asymmetry or weakness.1718 Sometimes it just hurts, even though the knee — indeed, the whole leg — seem to be healthy in every way that we can measure knee health. And if that seems a bit odd, you ain’t seen nothing yet!
Even when the joint is degenerating…
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Thanks to Dr. Scott Dye for helping me to understand and believe in my own unconventional ideas about patellofemoral pain syndrome, and by extension every other joint problem.
Extra special thanks to Tony Ingram, for substantial contributions of expertise and writing to this book in 2014 — the book is much better for it.
This document and all of PainScience.com was, for many years, created in my so-called “spare time” and with a lot of assistance from family and friends. Undying thanks to my wife, Kimberly, for countless indulgences large and small, and for being my “editor girlfriend”; to my parents for (possibly blind) faith in me, and much copyediting; and to Mike Gobbi, buddy and digital mentor, for many of the nifty features of this document (hidden and obvious). And thanks to all of the above, and many others, for many (many) answers to “what do you think of this?” emails.
Thanks finally to every reader, client, customer, and big tipper for your curiosity, your faith, and your feedback and suggestions and stories. Without you, all of this would be pointless.
The 2nd “edition” of the PFPS tutorial was launched on July 28, 2014, after months of collaboration with Tony Ingram, a Physical Therapist who did his Masters thesis on anterior knee pain. Tony was officially a co-author for a while, but retreated to focus on pursuing a PhD and a career in science.
Like all my books, this one was updated many times over the years, but changes were too small and spread out to constitute an “edition”: that had to wait for this, by far the largest ever major change to the book. It has several new sections, a lot of new science, and a strong (and overdue) new emphasis on the evidence-based value of exercise — reversing my grumpy anti-exercise position. It’s also much less exclusively about a single theory of knee pain than it was.
A new position on exercise
Exercise for patellofemoral pain syndrome is a good example of a treatment that works, but probably doesn’t work how most people think it works. I was anti-exercise before because the evidence just wasn’t there for it yet, and too many professionals fancied that they were prescribing exercise to change biomechanical parameters (e.g. patellar tracking) that correlated poorly with the condition. Such prescriptions tended to be overzealous: too much exercise, too soon for patients suffering from what is fundamentally an overuse condition.
Now there is good evidence that exercise is effective — hallelujah, some much-needed good news — but dosage and timing are key, and the biomechanical rationale still needs to be taken out with the trash.
Not just one guy’s theory any more
The previous version of the book had a significant weakness, a major idea about the nature of the beast (basically the whole “it’s the homeostasis, stupid,” ). The idea was plausible and elegant, but lacked adequate scientific support for an important basic point of the book. One advanced reader complained:
I didn’t buy your book so I could get one guy’s theory about how patellofemoral pain syndrome works.
Fair enough. She went on to say that it was probably a pretty good idea, just painfully unsupported. Simple as it is, that’s one of the best single constructive criticisms I’ve ever received. On the one hand, I unapologetically offer my take on these complex subjects. They are my books, and this is not a medical journal. On the other hand, I don’t want my take to be based solely on private speculation — if my opinion is to have much value, it should be clearly based on a diversity of expert and scientific sources. And so this is one of the major repairs in the 2nd edition. My basic point was sound, but badly needed some scientific and more diverse expert support — and now it has that.
“The pathophysiology of patellofemoral pain: a tissue homeostasis perspective,” an article in Clinical Orthopaedics & Related Research, 2005. This article by Scott F. Dye, MD, an orthopaedic surgeon from San Francisco, was by far the most influential source for this article. I do not normally recommend scientific articles to my readers, most of whom are ordinary people with knee pain, and not especially interested in slogging through medical jargon. However, in this case, I have to make an exception: although Dr. Dye’s writing is certainly intended for a professional audience, patients should still be able to get something out of it. It’s clear (for a scientific paper) and sensible, and even somewhat visionary in tone. Despite the fact that it’s certainly harder reading than this article, and despite the cost — the article will set you back US$10 to access — I still think it’s worth it. If you really want a good depth of understanding of PFPS, it’s required reading.
There are other kinds of knee pain, and it’s not always easy to tell which kind you’ve got. In particular, the two main types of runners knee are often confused. Tell them apart with this quick guide and checklist: The Runner’s Knee Diagnostic Stand-Off.
The journal American Family Physician publishes free tutorials for doctors which may also be useful for patients. I have come to trust those tutorials as one of the best sources available when I am trying to understand conventional medical opinion. They are usually well-written and beautifully illustrated, and determined patients can often get plenty of value out of them despite the jargon. See “Patellofemoral pain syndrome: a review and guidelines for treatment” for a 1999 tutorial for doctors, and “Management of patellofemoral pain syndrome” for their 2007 article on the subject. Bear in mind that these articles present only the conventional wisdom, however, and primarily discuss structural explanations for knee pain. As such, I do not think that they are useful to my patients and readers except as the best available representation of conventional wisdom.
The original publication date of this tutorial has been lost, but I think it was in 2004. It was quite rudimentary until 2007, when significant upgrades began. This change log was started in May 2007, along with many major improvements. As you can see, the tutorial has been updated many times since, and remains a live document.
Regular updates are a key feature of PainScience.com tutorials. As new science and information becomes available, I upgrade them, and the most recent version is always automatically available to customers. Unlike regular books, and even e-books (which can be obsolete by the time they are published, and can go years between editions) this document is updated at least once every three months and often much more. I also log updates, making it easy for readers to see what’s changed. This tutorial has gotten 75 major and minor updates since I started logging carefully in late 2009 (plus countless minor tweaks and touch-ups).
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New edition () — Major revision of the book with the help of, Tony Ingram, PT, MSo. The new edition has a few new sections, a strong new focus on the value of judicious exercise therapy, and updated and expanded citations for many key points. Read more about the 2nd edition.
New section (, section #8.11) — Expanded the section so much that it’s effectively new. It was just a single paragraph about orthotics. Now it is a much more thorough discussion of orthotics, shoes, and impact reduction. In particular, it features an unusual endorsement of Oesh shoes.See section #8.11, Orthotics and shoes.
Minor update (, section #1) — Added a reference about the poor overall quality of online information about common injuries. See Starman.See section #1, Introduction.
Major update () — Major improvements to the table of contents, and the display of information about updates like this one. Sections now have numbers for easier reference and bookmarking. The structure of the document has really been cleaned up in general, making it significantly easier for me to update the tutorial — which will translate into more good content for readers. Care for more detail? Really? Here’s the full announcement.
This report on two year’s worth of injuries among Vancouver runners — many of whom I probably run with every day on Vancouver’s sea wall — found that “patellofemoral pain syndrome was the most common injury, followed by iliotibial band friction syndrome, plantar fasciitis, meniscal injuries of the knee, and tibial stress syndrome.”
In 2010, the Journal of Bone & Joint Surgery reported that “the quality and content of health information on the internet is highly variable for common sports medicine topics,” such as knee pain and low back pain — a bit of an understatement, really. Expert reviewers examined about 75 top-ranked commercial websites and another 30 academic sites. They gave each a quality score on a scale of 100. The average score? Barely over 50! For more detail, see Starman et al. BACK TO TEXT
The science of this controversial claim will be discussed in great detail below. BACK TO TEXT
Sports medicine specialists are probably the least of all evils — although no professional category seems generally well-informed about PFPS, you probably stand a somewhat better chance of getting competent help from a sports medicine doctor than from any other kind of health care professional. Although they are more or less as prone to the toeing the line of conventional wisdom as any other health care professional, at least their expertise is directly concerned with non-surgical management of conditions like PFPS — and so there is at least some respectable chance that a doctor in this speciality will have paid some attention to the scientific controversies. BACK TO TEXT
Orthopaedic surgeons are surgeons — not only do surgeons strongly tend to perceive musculoskeletal problems only in terms of surgical solutions, but they are (quite correctly) professionally preoccupied with their surgical expertise and professional development, which means that they are typically not knowledgeable about conservative physical therapy methods for relatively minor overuse injuries like PFPS. Many of them certainly try to make a professional point of avoiding the overprescription of surgery, but that doesn’t necessarily make them experts in what to do instead of surgery. And PFPS is a particularly bad problem to take to a surgeon for the simple reason that, among knee injuries, PFPS is just about the last one that you’d want to operate on. This will be fully explained as we continue with the tutorial. BACK TO TEXT
Surgeons often oversimplify patellofemoral pain syndrome as simply a case of “arthritis” of that joint, and recommend a debridement (filing or smoothing) of the knee cartilage, either of the patellofemoral joint, or of the main joint between the tibia and femur (which is particularly irrelevant to patellofemoral pain). However, debridement has been proven to be ineffective even for arthritis (let alone PFPS, which isn’t arthritis), originally and most spectacularly by Moseley in 2002, then most authoritatively by The Cochrane Collaboration in early 2008 (see Laupattarakasem), and most recently by New England Journal of Medicine in September 2008 (see Kirkley). This is one of the most straightforward scientific slam dunks in surgery research in recent history — surgical debridement doesn’t work!BACK TO TEXT
There isn’t even a reasonably reliable surgical Plan B for patellar pain, as there are with several other common joint problems. BACK TO TEXT
As we’ll discuss in detail below, most “basic” physical therapy for PFPS consists of minor interventions of dubious value — mostly corrective exercises, stretching, ultrasound, taping and strapping — yet the clinical impression of most professionals is that mild patellofemoral pain does go away with conservative advice. The most likely explanation for this — and it’s a common “problem” in physical therapy — is simply that most of those cases would have gotten better regardless of the therapy. Of course, in some cases, some good advice may be mixed in with bad advice, and that may help. And there may be some placebo effect: being therapized really does help a lot of people to feel better, regardless of whether or not the therapy makes any sense, and yes this phenomenon can occur even with something as seemingly un-psychological as knee pain! See Moseley. BACK TO TEXT
In practice the diagnosis is more inclusive — as is this book, much of which is useful even for the patient who turns out in the end to have something a little better defined. BACK TO TEXT
Researchers tested 74 patients diagnosed with patellofemoral pain syndrome for the presence of several factor that are commonly suspected to be associated with that condition, the “usual biomechanical suspects”: muscle weakness and tightness, coordination, and postural and anatomical abnormalities. They also considered psychological factors, which is quite unusual for a study of knee pain.
They found no correlation at all with between the biomechanical factors and chronic anterior knee pain.
Interestingly, the researchers did find that “psychologic factors [anxiety and fear-avoidance beliefs about work and physical activity] were the only associates of function and pain in patients with PFPS.”