The squat as a foundational movement pattern and exercise is becoming more of a staple movement in physical rehabilitation, fitness and sports performance training. As this type of exercise gains in popularity, we should take a look at not only its benefits, but also its safety.
In my two previous blog posts about squatting, I presented the case that squats are safe and highly effective for building functional strength, and that your knees are allowed to travel past your toes as long as it's not to initiate the squatting movement. So, are deep squats bad for your knees?
"Avoid going below parallel" is another perspective or recommendation commonly given by fitness and healthcare professionals. On the other end of this polarizing thought, there is an increased trend of training deep squats in functional fitness and among less dogmatic healthcare professionals who understand squatting biomechanics. In order to figure out where to stand on the topic, we have to take a more pragmatic approach that looks at what's actually happening at the knee joint with deep squats.
First, let us take a look at a simplified version of the anatomy of your knee. The knee joint can be thought of as two joints: the tibiofemoral joint, and the patellofemoral joint. Your shin bone (tibia) and thigh bone (femur) interacts with one another primarily in a hinge like fashion. The backside of your knee-cap (patella) articulates within grooved surfaces at the end of your femur (femoral condyles). It acts as a pulley system for your quadricep tendon and muscles. The contractile tissues of this joint can be looked at the muscles and their associated tendons, which for the sake of simplicity will be the quadriceps, hamstrings, calf muscles, and glute muscles (indirectly). The noncontractile elements are the cruciate ligaments (ACL, PCL), the collateral ligaments (MCL, LCL), the menisci (medial and lateral), and the articular cartilage between the joint surfaces.
When performing a squat, increased forces or stresses are placed on various contractile and noncontractile tissues of the knee. Variables, such as external weight added, type of squat, and depth of squatting, can influence the amount and type of stress applied to the various tissues. Most often we are talking about shear and compressive stresses on the knee. The ligaments (ACL, PCL, MCL, LCL) are the primary resistors of shear forces; meanwhile, the cartilaginous structures (meniscus and articular cartilage) act to distribute loads from compressive forces. We must remember that the stresses are normal occurring forces that can promote healthy adaptations in the knee. Excessive and uncontrolled stresses are more of the concern when it comes to joint health.
In the image above, Dr. Aaron Swanson made a great diagram from a collection of biomechanical studies of different peak forces at the knee while performing a deep squat. There are a few key points that we can examine here. The ACL stress and anterior shear is highest with performing partial or half squats, and not during deep squats. The quadriceps and glutes are most active when going beyond 80 degrees of knee flexion, showing the benefits of deeper range squats from a muscle EMG standpoint. The quadriceps and the glutes play a significant role for both developing leg strength and providing dynamic stability of the knee joint.
But what about the peak compressive forces between 90-130 degrees in a deep squat? Yes, there is potential for increased compression in this position; however, let us remember that not all stress is bad. Progressive stress over time can build positive adaptations, such as thickening of cartilaginous structures. Also, a recent biomechanical study released in 2019 by Wu et. al has shown some promising research that suggests the safety of the deep squat position. The study shows that in deep squats beyond 120 degrees, the contact of the posterior leg/thigh musculature (hamstrings and calves) can help reduce compressive forces on the patellofemoral and tibiofemoral joints.
Should everyone perform deep squats?
I do believe that all individuals should have the capacity to perform deep squats as a function of exercise or daily life activities. Squats below parallel have shown to be extremely effective in developing strength in the quadriceps and glutes. This not only helps with performance, but also with creating stability through the knee and entire lower quarter. Also, having the ability to deep squat proficiently can only help people get up from lower toilets and lower car seats as an added bonus.
But can everyone perform deep squats? While idealistically everyone should have the capacity to perform deep squats, not everyone may be appropriate for training deep squats. The biomechanical studies primarily look at individuals with relatively healthy knees and no pain. So under those conditions, yes all of these compressive forces become negligible. For those who have diagnosed knee compressive issues, deeper squats may not be the best option. They can however be progressed appropriately with the right training and rehabilitative programs.
Demanding the full deep squat (ATG “*** to grass”) as part of a movement standard is not always appropriate. The deep squat is a skilled movement pattern and takes time to develop. Having people squat to a standard medicine ball as a target is not beneficial for training a deep squat. All this is doing is giving an external target for people to practice their suboptimal squatting pattern. Squatting deep should be coached appropriately just like other movement skills in the gym.
With all this being said, do I think that deep squats are bad for the knees? Absolutely not. I have stated in previous articles that the exercise itself is not bad for you. Rather it's the poor training habits, joint health, and stability that may be what makes the exercise not appropriate for you. Under relatively healthy conditions with no pain, I truly believe that all individuals should have the ability to perform deep squats. If capable of performing the movement, deep squats should not be avoided for fear of causing harm. Proper technique, good training habits, and a steady progression are all key to long term health and performance. Remember this article is not meant to be given as medical device as much as being informative. If painful conditions exist, a thorough evaluation should be performed by a qualified healthcare professional who understands your sport or activity.
- Bryanton, Megan & Kennedy, Michael & Carey, Jason & Chiu, Loren. (2012). Effect of Squat Depth and Barbell Load on Relative Muscular Effort in Squatting. Journal of strength and conditioning research / National Strength & Conditioning Association. 26. 2820-8. 10.1519/JSC.0b013e31826791a7
- Hartmann, Hagen & Wirth, Klaus & Klusemann, Markus. (2013). Analysis of the Load on the Knee Joint and Vertebral Column with Changes in Squatting Depth and Weight Load. Sports medicine (Auckland, N.Z.). 43. 10.1007/s40279-013-0073-6
- Salem GJ, Powers CM. Patellofemoral joint kinetics during squatting in collegiate women athletes. Clin Biomech. 2001;16:424–430
- Wu, John & Sinsel, Erik & Carey, Robert & Zheng, Liying & Warren, Christopher & Breloff, Scott. (2019). Biomechanical modeling of deep squatting: Effects of the interface contact between posterior thigh and shank. Journal of Biomechanics. 96. 109333. 10.1016/j.jbiomech.2019.109333
Disclaimer: The views expressed in this article are based on the opinion of the author, unless otherwise noted, and should not be taken as personal medical advice. The information provided is intended to help readers make their own informed health and wellness decisions.