By: Liz Zeutschel, PT, DPT, SSC
If you remember from Part 1 of this series, I said that “if you can squat, you should squat.” So does this exclude the 1 in 4 adults who experience frequent knee pain, or the person missing their ACL, or the older adult with arthritic joints? Are these conditions that preclude them from the many benefits of squatting? Absolutely not! Not every person will be able to walk into the gym on day 1 and squat below parallel with a barbell – and that’s okay! If you can sit and stand up from any chair, you can adapt the squat to your ability level. And, contrary to what you may have been told, you’d actually be doing your knees a favor.
Part 2—Taking Down the Knee Naysayers
Tell me if this sounds like you…
“I can’t squat down all the way because I tore my ACL.”
“My knees are too worn out from when I was young, and squatting will wear them out even more.”
“You’ll wreck your knees squatting with all that weight!”
As a physical therapist, if I had a dollar for every time I heard a colleague demonize squats—especially below parallel—I could probably have paid for my Starting Strength seminar. While I have the utmost respect for the profession of Physical Therapy, few physical therapists have actually lifted a barbell before and fewer still have explored the physics and biomechanics of a properly performed squat to the extent that a Starting Strength Coach has. This despite holding themselves out as the industry experts in all things exercise related. And while many physicians are quick to prescribe exercise to their clients with osteoarthritis or persistent knee pain, they don’t have the time or experience to adequately instruct their patients on exactly what that exercise should include. So they tell them to just keep gardening and walking around the mall.
If you remember from Part 1 of this series, I said that “if you can squat, you should squat.” So does this exclude the 1 in 4 adults who experience frequent knee pain, or the person missing their ACL, or the older adult with arthritic joints? Are these conditions that preclude them from the many benefits of squatting? Absolutely not! If you can get on and off the commode, you can squat. And, contrary to what you may have been told, you’d actually be doing your knees a favor. So, what might have you been told about squats and your knees? Let’s dive in!
Myth #1 – Squats Are Bad For Your Knees
To some people, squats look scary. And to people who battle knee pain or have suffered knee injuries, squats can be downright terrifying. But removing how they “look” from the question, we have to examine this myth by first identifying what it means when someone says squats are “bad for your knees.” Presumably, they are concerned over the possibility of injury or damage to the structure and function of your knee joint. The knee joint is where the femur and tibia meet in a fibrous capsule, containing cartilage, menisci, bursae, ligaments, and synovial fluid. In general, when someone is concerned about injury to the knee joint they are worried about damage to the soft tissues or a “wearing out” of the bone or cartilage components. When we examine how these structures function in a properly performed squat, you can see that there is nothing to be afraid of when it comes to squatting and knee health.
Deep squats do not place unwanted stress on your ligaments.
The moment of greatest muscular force acting on the knee joint during any kind of squat happens as the lifter switches from going down to going up. The leaned-over, hips-back position at the bottom of a low bar squat to full-depth stretches the hamstrings more than they would be otherwise, and makes their angle of pull closer to 90 degrees to their attachment point on the posterior tibia, as compared to a partial squat. This means that the hamstrings are involved much more in both the eccentric (downward) and concentric (upward) portions of the movement. This is important because when the quadriceps muscle group contracts to extend the knee, its “pull” imposes an anteriorly directed force on the tibia via its attachment point on the anterior side. Unchecked, this kind of pull stresses the ACL. Because partial squats are hamstring-deficient and because they often involve much heavier loads, this anterior stress is greater. Deep squats, however, reveal the amazing symmetry by which the knee joint operates. The hamstrings’ pull from the increased range of motion directly opposes the pull of the quadriceps.
By maximizing the contribution of the hamstrings to the movement, we are balancing these two forces, and there is not sufficient shear force across the knee to overstress ligaments such as the ACL and PCL, which prevent anterior and posterior translation of the tibia, respectively. This is why hamstring strengthening via squats and deadlifts is extremely important in the rehabilitation of an ACL tear! Research has shown that during a squat the ACL is not loaded anywhere near its limit and that tibiofemoral shear forces are reduced with the lesser knee angle of a low bar squat. This means that even if you don’t have an ACL – you can squat!
Contrary to what it might look like, you are not “bouncing off your ligaments” at the bottom of a squat. The bounce that is observed as the lifter transitions from down to up is actually a muscular stretch reflex, or a strong muscle contraction in response to a stretch. As discussed above, the ligaments of the knee are not being overstressed in this position. So this bounce—the stretch reflex—is not only advantageous but perfectly safe.
If you remember from Part 1, we prefer a toes out, knees out stance. Although the thighs are not parallel in this position, the foot and knee of each leg are coplanar, or in line with each other. The knee is flexing and extending in one plane, as the happy hinge joint it likes to be. If your feet and knees are in line, there is no torsion at the knee, and your ligaments are safe.
Squats will not wear out your joints.
Quite the opposite, actually, in that they will make your joints stronger and more resilient. No coach in their right mind would take a brand new client, slap 300 pounds on their back, and tell them to squat all the way down. Anyone who can squat hundreds of pounds likely started at a weight much lighter than this and in small, steady increments, worked their way up over time. This allows the tissues in the body to gradually adapt as they recover from appropriate amounts of stress. This is how our bodies get stronger. Bones, muscles, ligaments, tendons, etc. adapt to and recover from the stresses placed on them. If we all agree that weight-bearing is necessary to maintain bone density (granted you don’t apply so much stress as to cause a fracture), why wouldn’t we demand our joints and muscles also undergo some stress if we want them to remain strong and healthy?
The development of degenerative conditions such as osteoarthritis (the thinning of intra-articular cartilage) is complex, multi-factorial, and not completely understood. But blaming loaded human movement for its development is unsubstantiated. Research does not support the notion that squats will wear out your joints. It does, however, support the use of squats as a safe and beneficial lower extremity strengthening exercise. Cartilage thins as a result of disuse, not as a result of training. Not only that, but training has been shown through research to not make arthritis worse, and to be better than not training when it comes to joint health. Your cartilage is more likely to be “injured” as a result of immobility than training.
Myth #2 – Partial Squats Are Better For Your Knees Than Deep Squats
I already expressed my disdain for partial squats in the last article of this series, but in case I didn’t already convince you to squat below parallel, let’s go a bit deeper (no pun intended). The obvious reason that most serious trainees dislike partial squats is that they allow the use of more weight than a lifter would otherwise be able to handle below parallel. This not only increases your risk of injury in the gym but also feels a bit insulting to those of us who have worked hard to squat all the way down. But if we look at it more closely, we find that partial squats might cause more issues than they solve if you’re attempting to spare your knees in the process.
Partial squats are knee-dominant; deep squats are hip-dominant.
The depth to which you squat influences how leaned over you will be, which changes the amount of moment force applied to the hip and knee joints. Moment force is the force imposed by the weight of the barbell that is trying to bend (or rotate) your joints and crumple you into a heap on the floor. You can tell how much moment force is on a given joint by looking at the horizontal distance between the joint and the downward force vector from the barbell. The greater this distance, the greater the moment force. By not going all the way down, the back angle stays relatively vertical and moment force on the hip is reduced, decreasing the contribution of the hip extensors. This shifts the burden of force production to the knees, and since the quadriceps are producing most of the force required to move the weight, anterior shear force across the knee is increased. A partial squat also largely leaves the hamstrings out of the movement, so the posterior balancing force on the tibia is no longer being provided. (See Myth #1 above.) In order to reduce intra-articular forces within the knee, squat all the way down, with weights that you can handle below parallel, and use your hips!
Myth #3 – Your Knees Should Not Go Past Your Toes
Confession: I am guilty of fully believing this myth early in my Physical Therapy career. I instructed many patients to perform squats with their weight in their heels so their knees would not go in front of their toes. There, I said it. While we do want the feet planted firmly against the floor with the hips reached back, it’s not necessarily true that the knees should never pass the toes. For some people they will, and for some they won’t. But why?
The knees must travel forward in order to reach full depth, and their final position will depend not only on where the bar is held, but on the individual lifter’s proportions. A person with longer legs relative to their torso will see more forward knee travel than a person with shorter legs. And a lifter performing a front squat will see more forward knee travel than when the same lifter performs a low bar squat. The goal is to keep the weight centered over midfoot, the knees shoved out, the feet flat, and to reach depth just below parallel. If your stance is set correctly and these criteria are satisfied, your knees will be in their proper position relative to the toes. There is no evidence to suggest that letting the knees travel forward of the toes increases the stress on the knees to levels that are unsafe.
Trying to hold the knees back when they want to move forward means the lifter will have to make some adjustments in order to stay balanced. By not letting the knees move forward, the lifter’s shins will be excessively vertical and his weight behind midfoot, which is not as stable a position as with the weight centered directly over midfoot. Now, in order to stay balanced, more of his upper body mass will have to move forward, meaning he will lean over excessively as he descends, especially as the weight gets heavier. This puts a much greater burden of force production on the hips than there would be otherwise, decreases the contribution from the quadriceps, increases the moment force on the back segment, and makes it more difficult to achieve depth. If the back angle remains too vertical, on the other hand, the knees will travel excessively forward, with the weight shifting to the toes, and the burden of force production shifting away from the hip extensors and more to the quadriceps. Neither situation is ideal, but not because of the exact knee position, specifically. They’re less than ideal because the lifter no longer has his center of mass directly over his midfoot, and he has decreased the ability of one or more muscle groups to contribute to the lift.
If the feet are flat, the weight is balanced over midfoot, and proper depth is achieved, your knees will still be well within the limits of the amount of stress they can handle, and their final position will be determined by where the bar is held and how long your individual body segments are – not by where you think they should be.
Not every person will be able to walk into the gym on day 1 and squat below parallel with a barbell – and that’s okay! If you can sit and stand up from any chair, you can adapt the squat to your ability level. Maybe you start with just your bodyweight. Maybe you have to start by squatting to a high box and work your way down over time before adding weight. Maybe you will always squat with a box behind you. Whether you have a torn ligament, a torn meniscus, arthritis, or your knees are just plain weak, one thing is for certain: Squats are one of the best things you can do for them. And it doesn’t really matter where you start; what matters is that you start somewhere and then progress yourself over time for stronger, healthier, more resilient knees!
Last but not least, don’t miss the final part of this series where we tackle three common myths about squats and your back. Surely squats can’t be all that good for your spine… right? Stay tuned to find out!
Gotcher, CJ. Strength and Joint Health.; 2018. Available at: https://startingstrength.com/video/strength-and-joint-health-pt-3 (Accessed December 11, 2018).