Sensible advice for aches, pains & injuries

The Runner’s Knee Diagnostic Stand-Off

How to tell the difference between the two most common kinds of runner’s knee: IT band syndrome versus patellofemoral pain

updated (first published 2007)
by Paul Ingraham, Vancouver, Canadabio
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 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 memore about

This brief guide and checklist will quickly help most people with runner’s knee pain figure out which kind you have, and then forward you on to (much!) more detailed information for the diagnosis that fits you best. There are two common types:

  1. pain on the side: iliotibial band syndrome (ITBS)
  2. pain on the front: patellofemoral syndrome (PFPS)

There are other causes of knee pain, of course, but most knee pain in runners is one of these two suspects. They usually don’t occur together, but it can happen — to the unusually unlucky.

Diagram of the knee showing IT band syndrome on the side of the knee, and patellofemoral pain syndrome on the anteriorof the knee.

Where’s the pain?

IT band syndrome dominates the side of the knee. Patellofemoral pain is more variable, but usually more in front.

I’m a science writer and amateur athlete in Vancouver, Canada. I’ve been studying both of these knee conditions for many years now, ever since I suffered and recovered from an unusually severe case of IT band syndrome. In this article:

Knee pain in runners is usually no big deal, but it can get ugly

Both kinds of runner’s knee are repetitive strain injuries. Humans are indeed born to run in many ways, but we’re certainly not indestructible, and every marathon generates a bunch of new cases. They are usually easy to recover from: most people just need a little rest, some stretching that’s probably just a placebo, and maybe a change in running style. But mostly rest.

Unfortunately, both conditions do have a nasty tendency to become chronic and extremely frustrating in a few unlucky runners. When the pain is new, it’s impossible to know which way it’s going to go. Maybe it will go away quickly … and maybe it won’t. So it’s a great idea to be well preparedMaybe it will go away quickly … and maybe it won’t. So it’s a great idea to be well prepared and well informed just in case, because stubborn cases of both conditions are shockingly hard to get good help for. Both are misunderstood and mistreated by most doctors and therapists. They know the conventional wisdom … but much of that is wrong.

Many runners with knee pain don’t prepare for the worst. They get help slowly — if at all — and then weeks later realize they aren’t getting good help. By that time, their training schedule is blown to hell.

Front or side? Tell the difference at a glance

The easiest way to tell the difference between the two conditions is simply by the location of the symptoms. PFPS affects the kneecap and surrounding area, whereas ITBS definitely affects primarily the side of the knee (that’s the outside, facing outwards). PFPS may be felt in a wider area, but will still have an epicentre at the kneecap. ITBS will rarely spread much beyond its hot spot on the side of the knee.

PFPS has a broad scope: it is a “condition of conditions,” with many possible variations and causes. In many cases, a more specific diagnosis is possible, but it’s considered PFPS if a more specific diagnosis cannot be found.

ITBS has a narrow definition: it refers only to strong pain on the side of the knee, at or just above the lateral epicondyle. Pain that is primarily in the hip or thigh is something else, no matter how passionately you believe otherwise. For more about this common point of confusion, see Iliotibial Band Pain: Location, Location, Location!.

“Ow! Damn! The side of my knee hurts!”

— every single IT band syndrome victim ever

Diagnose your runner’s knee: a big comparison checklist

Note the knee symptoms that apply to you. Whichever side has more, place your bet on that diagnosis.

Check the knee symptoms that apply to you. Whichever side gets more checks … place your bet on that diagnosis. Check all that apply. (Note: this is not a form, you do not have to “submit” it … just count checks!)

Iliotibial Band Syndrome
Patellofemoral Pain Syndrome
The epicentre of the pain is on the side of the knee. Symptoms may occur nearly anywhere around the entire knee, particularly in severe cases, but the worst spot has to be on the side of the knee. The epicentre of the pain is somewhere under or around the kneecap. As with ITBS, symptoms may occur nearly anywhere, but it will usually be mainly on the front of the knee.
There is a spot on the side of your knee, right around the most sticky-outy bump, that is sensitive to poking pressure, but your kneecap is not particularly sensitive when pushed firmly straight into the knee. It’s not very comfortable pushing your kneecap straight into your knee, but there is no particularly sensitive spot on the side of your knee.
Pain tends to be worse when descending stairs or hills, and is either not painful at all or noticeably less painful when ascending. Pain tends to be worse when ascending stairs or hills, but may be painful both ascending and descending.
Pain first started while going downhill. Pain first started while going uphill.
Both PFPS and ITBS can start over the course of a few hours or a day, but ITBS almost always does. If the pain started relatively quickly, check this box. If your pain grew relatively slowly, over months or years, check this box.
Doing a deep knee bend does not especially hurt. Doing a deep knee bend definitely hurts.
Pain is not particularly affected by sitting, although it might get worse after sitting for quite a while (longer than an hour). Pain is clearly aggravated by sitting with knees bent. When you get up, it hurts more than it did when you sat down.
You do not have any obvious structural problems in the legs. You are a little knock-kneed, have flat feet, or kneecaps that seem to be kind of at a funny angle.
Symptoms tend to be quite consistent and predictable, with only minimal changes in the intensity of the epicentre over time, and almost no change in the exact location of the hottest spot. PFPS may also have consistent symptoms, in which case you can’t really check either side for this point. However, if you experience seemingly mysterious fluctuations in intensity or location — if you find that the problem is just not very predictable — this is a strong indicator that you have PFPS, not ITBS, so you should check this side. has very detailed tutorials about each of these knee pain conditions. Now that you have a better idea what kind of knee pain you have, read more about it. Much more! (Fun fact: after publishing this document for nine years now, I have quite good statistics on it, so I know that 60% of visitors will choose to read more about ITBS, and 40% will choose PFPS.)
Continue reading about
iliotibial band syndrome
Continue reading about
patellofemoral pain syndrome

Symptoms that don’t fit either ITBS or PFPS

It’s possible to have more than one significant knee condition at once, of course — including both ITBS and PFPS. However, it’s unusual. Here is a short list of symptoms that you should not see with either ITBS or PFPS:

Shouldn’t you get your knee pain diagnosed by a health care professional instead of here on the “internets”?

Yes. And that would be the right thing to say in a legal disclaimer. And I do. And the internet is a mind-bogglingly bad place to get this kind of information. Almost everything I’ve ever seen published on the internet about runner’s knee is wrong. Which is pretty much why I’ve spent years creating this website.

“Duty Calls”

xkcd #386 © by Randall Munroe

But the sad truth is that a lot of knee pain is misdiagnosed by professionals so often that you are just as well off — probably better off — starting with a detailed and referenced self-help guide.

Of course, if your symptoms don’t seem to match either column very well, then it probably is a good idea to consult a professional. ITBS and PFPS are not the only causes of knee pain!

But if you fit one profile or the other fairly well, then you can trust this diagnosis as a starting place. It’s based on many (nineteen) years of study and experience writing and teaching about runners’ injuries. This website is devoted to offering the most level-headed, evidence-based information possible.

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer, former massage therapist, and I was the assistant editor at for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.

What’s new in this article?

Improved some formatting, especially on mobile.

Much more reading about IT band pain and patellofemoral pain