Sensible advice for aches, pains & injuries
Anatomical illustration of the lower half of a man, dissection revealing the muscles only, highilighting the vastus medialis parts of the quadriceps muscle group, on the inside of the thigh.

Patellofemoral Pain & the Vastus Medialis Myth

Can just one quarter of the quadriceps be the key to anterior knee pain?

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

(No time to read this? Just apply Betteridge’s law of headlines! “Any headline that ends in a question mark can be answered by the word no.” So, no, vastus medialis is not the key to patellofemoral pain — it can’t be. But it is interesting to explore the reasons why…)

The most knee jerk exercise prescription for patellofemoral syndrome (PFPS) is to strengthen not just the quadriceps but one measly quarter of the quads. Practically everyone who seeks professional care for the condition gets told to specifically train the vastus medialis obliquus (VMO) muscle — the section of the quadriceps that is on the inside of your thigh, which pulls on the inside edge of your kneecap. This is widely regarded as the gold standard of therapy for patellofemoral pain. It needs to be demoted.

Quadriceps strengthening is actually an effective treatment,1 just not because of the VMO — but in countless cases the VMO gets the credit when general thigh training is what did the trick. Exasperating!

Meet the quadriceps

The quadriceps muscle is actually four muscles that merge at the kneecap (hence the Latin “quad”). There’s the fairly skinny rectus femoris section on top, and then three big vasti sections on the outside, centre, and inside of the thigh: the vastus lateralis, vastus intermedius, and medialis. The kneecap’s position is partially determined by the “tug-of-war” between these muscles. Alleged tracking problems, with their unknown (but probably trivial) significance, occur in theory because either the vastus lateralis is pulling too strongly, or because the vastus medialis is pulling too weakly, or a bit of both, or due to a problem with the timing (coordination) of contraction — for instance, both sides may be strong enough, but if the contractions aren’t well coordinated the effect may be asymmetrical. And so on.

The clinical significance of tracking has already been debunked earlier in this book. (Eh? What book?2) As discussed there, Peeler et al found that there is “no significant correlation between any of VM insertion length, VM fiber angle, limb alignment, and patellofemoral joint dysfunction location and severity [of pain].”3

Road sign as a metaphor for bad patellar tracking, with an arrow pointing ahead to

Pain if your kneecap goes off course? Seems logical…but it ain't necessarily so.

Similarly (as beaten to death in the chapter “Weak and uncoordinated muscles, perhaps?”) studies have found no differences in the timing activity of the VM in people with PFPS compared to those without, and any decrease in size or strength can easily be attributed to disuse because of pain — not vice versa.

But here’s the punchline, the coup de grace on this topic, the final VMO uh oh

It’s biomechanically impossible to exercise just the vastus medialis

It’s like trying to do a squat using just your butt muscles but no hamstrings — good luck with that. VMO isolation is a pernicious myth.

You can’t “isolate” the vastus medialis.4 Can. Not. You cannot avoid also exercising the rest of the quadriceps. It’s like trying to do a squat using just your butt muscles but no hamstrings — good luck with that. VMO isolation is a pernicious myth. “The concept of VMO isolation through specific exercise should no longer be part of our lexicon.”5 It’s also a deliciously good example of how the wrong “story” about what’s wrong leads to bogus treatment choices — and truth remains obscured because the intervention generally has positive effects for completely different reasons! Any benefits reported from VM training are due to exercising the quadriceps as a whole — not targeting the VM.6

A study conducted by Laprade et al. showed similar results using isometric exercise. This study compared the EMG activity in individuals with PFPS and asymptomatic controls during 5 isometric exercises. There was no significant difference in the ratio of VMO:VL firing between the two groups. Given these results, I find it hard to support the use of VMO training in everyday clinical practice.

~ Dr. John Snyder, PT, DPT, CSCS

In any case, the whole “weak and uncoordinated muscles” idea makes PFPS sound like the awkward lanky teenager of knee problems. Which is not true — many elite athletes with strong and coordinated legs get this problem! The baseline activity of a muscle is not determined by its maximal strength. Otherwise, bodybuilders muscles would be seizing them up and tearing their muscles from their bones. Muscles contract to provide just the right amount of force for a particular task, using both the commands of the brain and the feedback of the senses. How this all works is the endlessly interesting field of study called motor control. But all you need to know is this: just because a car is capable of going fast, doesn’t mean it always goes fast. I just can go faster, if needed. Think of muscles similarly.

The applicability of this lesson is important: just find a way to strengthen the knee that doesn't provoke more pain. Don't worry about targeting specific muscles or angles!

Knee pain won’t go?

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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.

Related Reading

This article is a free chapter from’s huge patellofemoral pain syndrome (PFPS) tutorial, one of 96 chapters in all. There are also several other articles on about patellofemoral pain and related topics:


  1. Kooiker L, Van De Port IG, Weir A, Moen MH. Effects of physical therapist-guided quadriceps-strengthening exercises for the treatment of patellofemoral pain syndrome: a systematic review. J Orthop Sports Phys Ther. 2014 Jun;44(6):391–B1. PubMed #24766358.

    This 2014 systematic literature review set out to summarize the evidence on quads training for PFPS, sorting through the junk to find 7 of the highest quality studies published at the time. The conclusion was strongly positive, clinically significant as well as statistically significant. Note that this study also found that pretty much any form of quadricep strengthing is effective, with no superiority for VMO-specific training. Just exercise those thighs!

  2. This article is an excerpt from an e-book about patellofemoral pain syndrome: Save Yourself from Patellofemoral Pain Syndrome! By coincidence, the tracking chapter I just mentioned is also available as an excerpt: see Patellofemoral Tracking Syndrome. BACK TO TEXT
  3. Peeler J, Anderson JE. Structural parameters of the vastus medialis muscle and its relationship to patellofemoral joint deterioration. Clinical Anatomy. 2007;20:307–314. BACK TO TEXT
  4. Mirzabeigi E, Jordan C, Gronley JK, Rockowitz NL, Perry J. Isolation of the vastus medialis oblique muscle during exercise. Am J Sports Med. 1999;27(1):50–3. PubMed #9934418.

    The purpose of this study was to selectively challenge the vastus medialis oblique muscle in comparison with the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles by performing nine sets of strengthening exercises. These knee rehabilitation exercise included isometric knee extension with the hip at neutral, 30 degrees external, and 30 degrees internal rotation; isokinetic knee extension through full range; isokinetic knee extension in the terminal 30 degrees arc; sidelying ipsilateral and contralateral full knee extension; and stand and jump from full squat. Electrical activity of the vastus medialis oblique, the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles was measured in eight uninjured subjects. Our study showed that isometric exercises in neutral and external rotation of the hip will challenge both the vastus medialis oblique and the vastus lateralis muscles. The results suggest that the electromyographic activity of the vastus medialis oblique muscle was not significantly greater than that of the vastus lateralis, the vastus intermedius, and the vastus medialis longus muscles during the nine sets of exercises. Results suggest that the vastus medialis oblique muscle cannot be significantly isolated during these exercises.

  5. Malone T, Davies G, Walsh WM. Muscular control of the patella. Clin Sports Med. 2002 Jul;21(3):349–62. PubMed #12365232. BACK TO TEXT
  6. Lee TQ, Sundusky MD, Adeli A, McMahon PJ. Effects of simulated vastus medialis strength variation on patellofemoral joint biomechanics in human cadaver knees. Journal of Rehabilitation Research & Development Vol. 2002 une 2002. PainSci #56868.

    From the abstract: “Treatment included iliotibial band stretching and patellar mobilizations that focused on stretching the lateral retinaculum. It may have been these latter treatments or strengthening of the quadriceps muscle as a whole that was responsible for the decrease in symptoms.” Indeed! This study suggests that vastus medialis muscle may have little effect on patellofemoral joint mechanism, although a study of living patients would be better than studying the dead knees of cadavers, as was done here.