Phone: 03 8822 3723

The Single Leg Squat Is The Best Exercise For Knee Injury Prevention

Written by: Nick Jack
Category: 2014
on 20 June 2016
Hits: 55876

Anyone who has had a severe or chronic leg injury, will know just how difficult it can be to do the simplest of movements or activities such as walking up stairs or getting in and out of cars. Even just regular walking itself can be hard! I should know, I have had more than my share of injuries. Most of my injuries have been on my left leg, and many of them could have been easily prevented if I had adopted the methods and exercise techniques I am going to share with you in this article. For these injuries were not bad luck, they were all postural and movement related. Plus the fact I did not rehabilitate them correctly and went straight back to playing sports, led to compensation and dysfunction, that created a new injury. Each time this happened I became much less stable, stiff at various joints and much weaker. It was only later in life taking on my current role, researching and learning from my mistakes, did I find the answer. And possibly the greatest answer has been the power of learning how to do a Single Leg Squat. In this article. I will show why we regard this so highly in both rehabilitation and injury prevention.

Where The Pain Is, Is Rarely Where The Problem Is!

I have covered this topic in great detail on a broad level once before in our article Why The Knee Has Nothing To Do With Knee Pain. This is in fact true for every type of chronic injury that was not caused by a traumatic accident but evolved for no reason. For knee problems the source of all these problems is two areas.

The hip/pelvis and the foot/ankle. A potential third consideration is the brain, more specifically coordination of movement.

It can be hard to say what started the ball rolling from a dysfunction point of view. Whenever there is a mobility restriction, or stability deficit at a joint there will be a chain reaction of multiple compensations in the body that will be easily seen in a single leg squat. From tight ankles, stiff hips to weak abdominal stabilizers, weak feet, weak glutes and poor movement mechanics. What is clear is that the longer the problem is left unattended the more severe the compensation becomes as the leak in the pipe so to speak spreads to other areas.

This means that the single leg squat holds a lot of clues as to providing the solution to problems. But even more importantly it contains the secret to preventing these injuries too!

If I was to use my own injury history to highlight this. Below is a list of all the injuries suffered by my left leg.

  • Severe ankle sprains 5 times!
  • Osteitis Pubis
  • Grade 2 Hamstring tear
  • Plantar Fasciitis
  • Achilles Tendinosous
  • Patella Tracking
  • Hip clicking and instability

I had a 5cm difference with measurement to my quadricep versus my right leg. Basically I was in a lot of trouble for a long time suffering setback after setback. In all these cases I had Physiotherapy treatment that included massage, stretching and some simple remedial exercises like calf raises or tubing exercise. All of these treatments helped to take my pain away and after a few weeks, I was able to get back to what I was doing, only to suffer another problem again in a few weeks time. During this time I never injured my right leg once!

I only managed to finally get on top of all these problems when I finally understood the importance of correcting my posture and learning how to move. (Which by the way was never taught or shown to me at any stage with all the different therapists I had seen). The most important thing I had to do was - learn how to move on one leg, for this is where all my issues were going to be found. I say this almost every day to my clients - "the activity or movement that is most likely to hurt you, is also the one you need to learn how to master". For if you master the one thing that can really hurt you, there is no real chance of being injured again!

My right leg during this time was completely free of any injury and it was not until I was 42 that I injured my right leg due to a freak slip in a basketball game and tore my ACL! I had to go through a complete ACL rehabilitation program the single leg squat was the key in putting it all together. I can tell you now that my right leg is as strong, if not stronger than before the injury from doing stacks of single leg drills.

But why are the single leg exercises so important?

Can't you just use simpler exercises like squats and traditional deadlifts? These are great exercises and they definitely help, but they lack exposing the stability deficits that will be revealed in single leg stance (more on this shortly). What about the leg press, leg extension, leg curl, calf raise etc etc to build strength into your muscles? Stronger means the joint is protected right? No, not at all. For I also tried this in the early days only to develop more problems. Like I said earlier, I had to learn how to move correctly, with great balance, timing and progressing to more difficult movements that would replicate what I needed in my job and sports.

Machine training is without doubt one of the worst things you can do for any injury, for it weakens stabilizers, neglects mobility requirements, and destroys good movement at the expense of trying to get strength. Watch our videos below explaining the danger or machine training and a second video explaining what stability really means to see detailed explanations of these concepts.


Let's Start With The Feet & Ankle!

If we start with the feet you will see just how important this is for you to look at if you have any kind of leg injury. And if you don't want to get one this is also a very important thing to understand.

Our feet are designed to do ABSORB shock and provide the ability to PUSH off the ground when we walk, run or jump. The foot needs to act like shock absorber or a spring. Problems arise if we lose either one of these two things, and ultimately lose our spring. This is where injuries will occur at other joints like the knee as the shock is sent up the lower limb from the feet to the next joint, which in this case is the knee!

Take a look at the picture below for an example of this chain reaction.

The big toe is a big part of the equation when it comes to providing stability in a single leg stance. Our power during propulsion which is what we need for walking, running and jumping is dependent upon the foot’s ability to become a rigid lever. Making sure you can flex your big toe is the key to achieving full foot supination which counters pronation. When you walk, the entire body is advancing past this single joint, the ability to dorsiflex, and then be able to raise the heel as you move through the various stages. If this mechanism fails, compensation will be forced to cheat at ALL joints from this point onward.

This is a massive topic on it's own and I suggest you read our full article on everything to do with feet to see how to assess and correct any dysfunction by going to this link - Exercise Solutions For Weak Feet

We also cannot ignore the ankle joint. Many people playing sports have suffered an ankle sprain, many multiple sprains. This joint unlike the feet that needs stability, needs a great degree of mobility! Prior sprains, poor footwear or even poor foot stability begins to stiffen the ankle joint. A tell tale sign of ankle restriction is the if person has restricted dorsiflexion (pulling your toes back towards your shin). Dorsiflexion is something we all tend to take for granted in daily life and in sport and trust me you can ask the people with walking impairments how hard it is to walk when your foot does not do this.

Every time you squat, lunge, and move your legs for almost any daily activity you require it. In sports even more so with high powered multi-directional movement patterns (eg, tennis, football, basketball etc), requiring high levels of ankle mobility to be able to move in several directions all in a split second, while maintaining perfect balance and control. The risk is much higher for this reason which is why any sportspeople who suffers recurring ankle ligament injury must have a strong focus on regaining optimal mobility as fast as they can.

A great article to read with stacks of detail about how to assess and also drills to use for mobility are in this article - How To Improve Ankle Mobility

Good videos of with ideas of how to integrate foot stability into the single leg movement are shown below.


It Is All About The Glutes!

It is funny that we are talking about the glutes (butt muscles) here and not the VMO or some quadricep exercise as most people are told to do for a knee injury.

Again people look too much at just the area in pain instead of looking at what caused the pain. And in 90% of all lower limb injuries we will find a weakness at the glutes. These large powerful muscles are also very lazy and easily dominated by hip flexors and quadricep muscles wanting to overwork. This is where the injuries are usually born, and over time through countless repetitions of loading the quads which become more and more dominant, and the glutes becoming weaker and weaker that the joints now become exposed to injury! 

Use of simple isolation exercises such as the Clam and Hip Extensions are great introductory exercises to use, read our article on How To Strengthen Glutes for detailed instructions on how to do this or get a copy of our FREE Glutes Checklist below.

What you must understand with all isolation exercises, and especially glute drills is that is all they are - "introductory exercises" only.

They are not even close to actually building enough strength or stability that is required for injuries like ACL ruptures or a tear. And they definitely will not prevent knee injuries. They are just a starting point. Remember earlier I said I had all sorts of trouble after Physio treatment when I went back to sports because this is usually as far as my rehab went. I was told to keep doing these and I would be right. But we all know what happened after that! The problem with the clam which many would regard as the best exercise for isolating the glutes, is it only uses one part of the glutes role. When in fact there are three parts that are used simultaneously in a movement like walking and running.

There is three distinct heads of the gluteus medius muscle that perform a unique role as the body moves:

  1. The posterior fibers - These fibers contract at early stance phase to lock the ball into the hip socket. The posterior fibres therefore essentially perform a stabilising or compressing function for the hip joint.
  2. The middle/anterior fibers - These run in a vertical direction, help to initiate hip abduction, this is where the clam comes in which is then completed by a hip flexor muscle known as the TFL. The glutes work in tandem with TFL in stabilising the pelvis on the femur, to prevent the other side dropping down.
  3. The anterior fibers - These allow the femur to internally rotate in relation to the hip joint at mid-to-end stance phase. This is essential for pelvic rotation, so that the opposite side leg can swing forward during gait. The anterior fibres perform this role with TFL.

Basically we need an exercise that performs these three key functions in order to restore optimal movement and strengthen correctly. The exercise needs to stabilize the hip, act as a hip rotator, and lock the head of the femur into the socket, creating a very tight and stable hip joint during gait. This prevents the ball and socket joint from rattling around during walking and running. Can you see now how the isolated glute exercises used extensively in rehab settings, Pilates programs and even machines to isolate and strengthen ignore these key principles and do not adequately strengthen and prepare the body for how it actually moves.

What exercise would use all three functions of the glutes?

You guessed it..... The Single Leg Squat! Here is how you do it and what to look for.

How To Do The Single Leg Squat & What To Look For


I highly suggest to watch the videos above as I take you through all the stages of what to do in the assessing stage and also what the common mistakes are. You will also find our article - How To Use The Single Leg Squat As An Assessment Tool an excellent resource for helping you in the assessment stage.

As we have already discussed the single-leg squat is superior to other movements for it uses all of the glute function but it also uses quadriceps, hamstrings, adductors and abductors along with help of core stabilizers and even the muscles around the ankle. This means that it is also a great test to use to determine where any leaks in the pipe may be hiding. It is always wrong to ignore a poor single-leg squat, as this movement shows you what will happen with the support leg during running. You might need the help of a friend or coach, or use a mirror to identify these mistakes. Video feedback is the best, as it gives great slow motion detail and you can draw over the screen. This is invaluable as a teaching resource with my clients, and even myself!

First let's define the technique.

Correct Technique:

  1. Begin the movement by flexing at the hip and continue bending the knee and ankle until your thigh is as close to parallel to the ground as you can get it.
  2. Keep hands in front of the body.
  3. Keep trunk as neutral as possible, preferably neck above toes, avoiding excessive lumbar and thoracic curvature.
  4. Heel must stay in contact with the ground at all times.
  5. And MOST IMPORTANTLY make sure you ankle, knee and hip all line up in a perfect straight line.

There are a quite few things that contribute to poor single-leg squatting so here is a table highlighting what to look for.

You Must Progress To More Difficult Movements For Long Term Success

Now that know the technique and are able to execute correctly you MUST progress this movement with various skills.

Strength is obviously one component but again it is only small piece in a puzzle of skills you need in order to be fully rehabilitated. Balance, Power, Agility are some of the more difficult skills to learn and ultimately where many answers lie. This is the mistake I made many times when I was younger by missing out on this type of training, so if you have read the article as far as here you are already miles ahead of me. Always remember you are constantly trying to force your body to adapt to new stimulus that is harder than what it can currently do. As long as it is safe and a gradual progression you will reap huge rewards.

Most sports require the ability to jump off one leg vertically, laterally (sideways) and also be able to stop suddenly and change direction. This means that you must expose your leg to these skills and be able to perform as close to perfect as possible in the gym for you to be safe in the real world. This is true also to some extent to non sports players for even the movement of getting in and out of a car is similar to a single leg squat sideways. Very difficult to do if you have trouble with a single leg squat. There are countless exercises and methods you could use if you are someone wanting to design a great injury prevention program for sports. Or even if you are recovering from a Knee Injury.

Below is two of our complete online programs that go into great detail for specific knee injuries like Patella-femoral tracking or ACL injury and you can get instantly as a Download by going to our online shop. Click the images below to see more about each of these advanced programs and get a copy instantly. Both have videos and pictures with instructions on how to assess and design a program specific to your body's needs.

But to help you out here is a quick look at how to use the single leg squat with progressions of strength, agility and power to give you an idea of how to the simple single leg squat sets the foundation for great movement that makes your legs bulletproof to injury!

Single Leg Stability 

To enhance foot stability and master the art of leg alignment I love using the Toe Touch Drill seen in the video below. The video on the right shows you several single leg squat regressions you can use to gradually ease your way towards strengthening.


Single Leg Strength Progressions

I will start with strength progressions for this is the easiest of the progressions to master. Once you have fully mastered the stability and movement skill stage it is good to add some additional challenges to the feet and the hip. For remember they were most likely the cause of all the trouble in the first place. The two videos below provide you with some great ideas here.


Single Leg Landing

This is where we introduce agility training! The challenge is much greater to the nervous system and the joints in trying to maintain perfect stability than strength for there is more moving pieces and things to stabilize. This prepares you for the next stage which is where you will begin to move laterally (sideways).


Single Leg Lateral Movement

Lateral movement is always the most challenging for knees and where most injuries will occur. To guarantee your knee can handle this movement it must be tested and prepared for it.



I am sure you can agree now that the single leg squat is by far the best exercise for not only assessing compensatory movements but a particularly great exercise in it's own right for strengthening the entire leg. The timing it shares with walking, running and many sports activities mean it has a great carryover effect of teaching the body how to move efficiently without pain and restriction. The overuse of isolated muscle exercises by many rehab programs is so disappointing when just simply learning how to move correctly could have done a much better job in half the time. Learning to progress to more difficult movements needing more skills such as balance, power and even agility is critical in taking your body's ability to new heights. If you play sports this should not be looked at as a luxury but an absolute necessity.

For more ideas and information on specific topics I may not have covered in detail be sure to check out our INDEX PAGE on the website that has over 300 of our best articles. These are all sorted into categories for quick reference so you can find what you are after more easily. You can also subscribe to our FREE fortnightly newsletter by clicking here.

If you do need specific help with your exercise program please feel free to reach out to me for help and we can set you up with your individualised program.


About The Author

Nick Jack is owner of No Regrets Personal Training and has over 15 years’ experience as a qualified Personal Trainer, Level 2 Rehabilitation trainer, CHEK practitioner, and Level 2 Sports conditioning Coach. Based in Melbourne Australia he specializes in providing solutions to injury and health problems for people of all ages using the latest methods of assessing movement and corrective exercise.


  • Movement - By Gray Cook
  • Corrective Exercise Solutions - by Evan Osar
  • Athletes Acceleration Speed Training & Game Like Speed - by Lee Taft
  • Diagnosis & Treatment Of Movement Impairment Syndromes - By Shirley Sahrman
  • Low Back Disorders - by Stuart McGill
  • Knee Injuries In Athletes - by Sports Injury Bulletin
  • The ACL Solution - by Robert G Marx
  • Understanding & Preventing Non-Contact ACL Injuries - American Orthopaedic Society For Sports Medicine
  • Anatomy Trains - by Thomas Meyers
  • Motor Learning and Performance - By Richard A Schmidt and Timothy D Lee
  • Assessment & Treatment Of Muscle Imbalance - By Vladimir Janda
  • Scientific Core Conditioning Correspondence Course - By Paul Chek
  • Advanced Program Design - By Paul Chek
  • Twist Conditioning Sports Strength - By Peter Twist
  • Twist Conditioning Sports Movement - By Peter Twist
  • Twist Conditioning Sports Balance - By Peter Twist