Know Your Numbers: The Face-Up Heel to Butt Test


Your wallet is stuck in your knee joint. ~Barefoot Rehab

The ability to differentiate a knee joint problem (the ‘ol wallet in the door syndrome) from a quadriceps muscle problem can save the knee from imminent surgery.

That’s what we’ll discuss here.

Mobility: Face-Up Heel to Butt Test | Supine Knee Flexion (SKF)

The ability to bring one’s heel to her butt is something that anyone should be able to do, when healthy.  The “Face-Up Heel to Butt Test”, or in mechanical terms, supine knee flexion, will let us know if you have that ability.

What do I need to Measure this Test? You will need a flat surface to lie on, a ruler, and a friend to help you measure this test.

What is the Face-Up Heel to Butt Test assessing? The mobility of your knee joint integrity. These structures include bone, ligaments, tendons, cartilage, menisci, and muscles (vastus medialis, vastus intermedius, and vastus lateralist).  This test is NOT testing rectus femoris.  To test rectus femoris, do the lunge stretch test while selectively tensioning the knee.

What Specific Dysfunctions are relevant here? Besides adhesion of the three structures that limit knee flexion, there are several knee pathologies that can permanently limit the range: osteoarthritis, joint inflammation, cartilage or mensicus pathologies will show up with this test.

Your friend can feel the different between muscle and joint by what the range of motion feels like at the end range.

  • A soft, springy end-feel = muscle restriction.
  • A hard, cement-life stop to your end-feel + “wincing” + a comment to your friend “slow down, be careful” = joint restriction.

What You Need to Know: If you have a joint restriction, don’t bother stretching any knee tissues.  You can stretch until the cows come home and your range of motion will not increase.  See a qualified therapist/healthcare provider before performing any activity with high knee load.

How to Test:

Lie on the ground. Your friend should take your leg and push your heel to your butt.  Have him/her be gentle with your leg, especially if you’ve had any knee joint issues or ACL/MCL/meniscus problems in the past.

If your heel is close to your butt, you can measure the distance from the butt with finger breadths (see below). If you’re very restricted, use a ruler to see how far your heel is from your butt.

Write this number down.  Any mobilization, stretching, or treatment interventions are attempts to increase this number.  If the number isn’t increased after a month, you’re wasting your time.


A pass for this test is the ability to bring your heel to your butt.

  • Range: Touching
  • Effort: Fast and easy.
  • Symptoms: No symptoms.  No symptoms includes the feeling of a stretch.  Ideally, there would be no stretch.


A fail with a low risk of injury is anywhere from the heel touching the butt to 2 finger breadths away.

  • Range: 0 – 2 finger breadths.
  • Effort: Fast and easy.
  • Symptoms: You may feel a pull in quad.  This is indicative of one of the vastus muscles having adhesion.


A fail with a high risk of injury is anywhere more than 2 finger breadths away.



  • Range: More than 2 finger breadths away.
  • Effort: May be slow, labored, or guarded.
  • Symptoms: Same as the “fail – low risk”.  You may feel a pull in the quad. This is indicative of vastus muscle adhesion.  This will be springy at the end range.  If it’s a hard-stop or if you wince, this is usually individual of a joint pathology (osteoarthritis, inflammation, cartilage, or meniscus issue).  If your range of motion is too much to even measure, I recommend you consult with a musculoskeletal specialist or surgeon before starting any movement routine that will stress your knees.

I Know My Numbers – What do I do now?

Insanity: doing the same thing over and over again and expecting different results. ~Albert Einstein

There are a plethora of mobility and stretching resources out in the interweb for you to experiment with. It is not our intention to give prescriptive answers, simply to bring awareness to where your body currently is in time.

Use whatever tools you’d like to use for a month, stretching about ten minutes a day, for three days a week, for a month.

After a month, re-test.

If you’ve gained range of motion, wonderful!  Wash, rinse, repeat, and continue stretching.

If you’re no more flexible or mobile than you were before, STOP THE INSANITY AND THE STRETCHING!  It’s now time to see a Manual Adhesion Provider or Active Release Technique Provider to diagnose your condition and potentially remove the adhesion in relevant tissue to restore your mobility before you go on layering strength on top of unhealthy tissue.


While you’re awaiting 30 days from now to reassess, you might as well get baseline measurements for your hip flexion, hip extension, ankles and your low back.

speechbubblesWhat are you numbers? Please share range, effort, and symptoms below and we can discuss what you should be doing to restore musculoskeletal integrity.

Dr. Chris Stepien, DC, Full-Body ART Certified, CSCS, and CrossFit Level 1 Certified, is a Sports Therapy & Chronic Pain Resolution Specialist with Barefoot Rehab and Cultural Instigator at Heroes Journey CrossFit in Parsippany, NJ.  Among the healing depressed, Dr. Chris uses highly-leveraged physical modalities such as manual therapy and community-based fitness to inspire people to rewrite their own stories, finding strength and happiness where there once was none.  Dr. Chris’s purpose in life is to help people understand their heel to butt test.


The post Know Your Numbers: The Face-Up Heel to Butt Test appeared first on Barefoot Rehab.

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