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The Truth on Fitness: Do I Have to Keep My Knee Behind My Toe?


Exercise Analysis

For the longest time, one of the basic rules of exercise has been to keep our knees behind our toes during ground-based exercises.  Apparently, allowing the knee to project past the toes while doing things like lunges, squats, and step-ups, creates too much stress, and is potentially harmful to the knee.

But is this true?

Actually, no.  Several research studies have demonstrated that allowing the knee to project as much as 10 cm beyond the toes during ground based exercises imposes no more stress on the knee than keeping the knee aligned over the ankle.  And those that insist on keeping the torso upright during these activities are really doing more of a disservice.

Exercise AnalysisFurther research has shown that by allowing the trunk to incline forward during ground based exercises, there is greater activation of the glutes and hamstrings.  That provides for a more effective workout, and enhanced, not diminished, stabilization of the knee.

So, instead of focusing on where the knee is in space, the better strategy is to shift your weight onto the center of your lead foot, in the case of a lunge, and allow the trunk to tilt forward.  Your knees will be fine, and your glutes will thank you.

For more information on knee alignment, read the full article here: The Truth on Fitness: Must the Knees Remain Behind the Toes.

Paul M. Juris, Ed.D.
Executive Director, CYBEX Institute for Exercise Science

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Dr. Juris earned his Doctorate in Motor Learning from Columbia University in 1993, followed by a variety of positions in higher education, rehabilitative medicine, professional sports, and fitness. Paul Juris, Ed.D. was named Executive Director of the CYBEX Institute for Exercise Science in January of 2007

Cybex is a provider and manufacturer of premium commercial fitness equipment.  Content featured in the Cybex Fitness Blog is meant to inspire healthy living and wellness and should not be taken as medical advice. For medical advice please consult a doctor. 



Hello. I would like to see the references that proved that. Thanks.
Posted @ Monday, August 08, 2011 8:58 AM by Karine
I am a fitness instructor on my own and was studying sport university. Tried variety of lunges & squats and I think keeping the right posture is very important for your knees & also for the lower back. Please do not misslead people to harm themself.
Posted @ Monday, August 08, 2011 9:01 AM by Adriana Sladek
Allowing the knee to translate forward does in fact place too big of a strain on the patella tendon and allows for the "slide, glide, and roll" effect of the femur on the tibia, leading to irritation of the meniscus. The movement itself is not to be considered taboo, but putting load, even bodyweight from a lunge or step up, will certainly lead to the weight being shifted to the toes, thereby disengaging the hamstrings and overloading the quads. Regarding the angle of the torso, a downward inclination would suggest a restriction in hip flexor mobility. And to properly engage the hamstrings an anterior rotation of the pelvic girdle must be accomplished, which is achieved naturally by lifting the chest in squatting movement. This is counter to the posture the pelvic girdle is allowed to do when tilting the torso down.
Posted @ Monday, August 08, 2011 9:06 AM by Rodney Fulmer
Please share the research articles supporting your opinion of knee position with CKC exercise. Thank you
Posted @ Monday, August 08, 2011 9:09 AM by Skip Stevens
You obviously have never squatted before. Go right ahead and let your knees glide forward as you squat (especially with heavy weight). Let me know how you feel after 6-10 sets of heavy singles.
Posted @ Monday, August 08, 2011 9:18 AM by KB
I Always knew that the rule of 'keep your knees behind your toes' was complete BS. 
It is Physically Impossible to Squat at all if your knees stay behind your toes. Gravity will Pull your Back-side backward down to the Floor! 
Therapists always told me, 'Act like you are about to sit on a stool.' How? Of there is no Stool, there is only Air- and from there your butt will fall down-- OR- you are only doing a half-assed Curtsey. It would be like doing Bicep Curls with only 2-inches ROM. 
I agree with avoiding meeting your butt to your heels when using weight...but avoiding ROM? No.
Posted @ Monday, August 08, 2011 9:58 AM by Jason
Jason - not an attack on you, but who taught you how to squat? You physically cannot squat correctly w/o sitting back. If you fall backwards, you aren't squatting correctly. I've been squatting for over 20 years, and have taught people to squat for over 10, and have yet to have someone fall backwards.
Posted @ Monday, August 08, 2011 10:05 AM by KB
10 CM forward of the toes is actually pretty far forward. My patellar tendon doesn't like that even with bodyweight lunges! I'd like to see your references and if there is more than one study that supports your position.
Posted @ Monday, August 08, 2011 10:09 AM by PJ Glassey
Thank you for the posts, if you'll take a few moments and read the complete article located in the Truth on Fitness section of the CYBEX Institute website, you'll see all of the citations from which this information came. 
If you read carefully, you'll see that the issue is not the position of the knee relative to the foot, but the position of the knee relative to the line of force. 
Escamilla points out very effectively, that performing wall squats, with the knee well behind the toe, imparts far more stress on the knee than a lunge with the knee 10 cm in front of the toe. 
This is shown consistently in other literature as well. 
Regarding squats, again, the issue is not knee position alone, but joint position relative to the line of force. In a properly balanced squat, hip and knee joint torques are roughly symmetrical, and the knee aligns slightly in front of the toe. Deliberate attempts to keep the knee behind the toe during a squat increases torque loading on the back and puts the lumbar spine at risk. 
None of this, by the way, is opinion. It is all supported by evidence. Please read and discover for yourselves.
Posted @ Monday, August 08, 2011 10:25 AM by Dr. Paul Juris
Obviously people are too focused on the knee. Lack of ability to squat/lunge/step-up correctly without knee pain is going to relate back to immobility in either the ankle or hips (or both). If the mobile joints above and below the knee can't move properly then yes, the knee (a stable joint) will be tasked with too much load. In the squat there should be a parallel line between the shin and the torso at the bottom of the movement. As well the top of the pelvis and the bottom of the rib cage should be parallel to each other; without that spine loading will be excessive (neutral spine will not be maintained) and thus the deep stabilizers of the spine will not be recruited properly. The knees are going to move forward without negative effect (unless due to poor movement mechanics you've already messed up a knee joint and are know trying to load an unstable joint). It isn't the squat that is the issue folks, it's your body.
Posted @ Monday, August 08, 2011 10:41 AM by VM
Dr. Juris: Thank you for this provocative article. I would encourage all interested to read the article and to, as clinicians bridge the gap between research and practice. I had to search a bit for the article to find the citations. The article is here:
Posted @ Monday, August 08, 2011 12:04 PM by AWeiler
Using Youtube as a starting point for technique? Not very credible. 
I'll buy into this paper as soon as you do these exact same exercises with more than body weight. Perhaps a backsquat with 300# or a lunge w/50# DB's or bar on the subject's back.
Posted @ Monday, August 08, 2011 1:42 PM by KB
I don't believe that having the knee travel slightly past the toes will cause any damage to the knee. The problem comes in where the knees travels excessivly past the knees, and the knees and toes are out of alignment. keep in mind also that everyone has a different range of motion. Proper alignment is more important than range of motion.
Posted @ Monday, August 08, 2011 2:21 PM by OB
I tore my MCL by not paying attention to my back leg during a lunge, I'd like to see some more data on this.
Posted @ Tuesday, August 09, 2011 4:33 PM by Christy
I would agree that in a free weight lunge such as a walking dumbell linge, leaning forward with a small cross over the lead toe and a drive backwards is very good. However of a free weight squat the knees would not cross over if done correctly. On a wall squat or smith machine it is very different and that should be addressed. You can do a lot of damage as the body is not free to move naturally so understanding this area is critical in training. Ask anyone who has squatted 300 - 400+ for many years and they will tell you the knees naturally flare out and stay just almost in line with the toes. Forward motioned reduce by bar positioning. Good article but perhaps a bit more specific in each exercise would be helpful.
Posted @ Wednesday, August 10, 2011 9:02 PM by Brian
Anyone who has worked with clients will know that each is different. Levers are different from person to person. So assess each client. Joint mobility is the key factor. And obviously the deeper you squat, the further your knees drive forward. The FMS teaches vertical posture in the split squat. Perhaps that is for assessment purposes only. A tilt forward would create an elastic response in the glutes and hamstrings thus engaging them. However, I want to see my clients control movement with good posture.
Posted @ Thursday, December 15, 2011 8:46 PM by Ty
The knee over the toes is a natural movement. Just watch a small child when they squat. As for all of those that still preach not to let your knee go over your toes need to read the research.
Posted @ Friday, September 14, 2012 3:56 PM by Gary Jacque
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